libstdc++: Remove dg-options "-std=gnu++20" from <concepts> and <ranges> tests

The testsuite will automatically select C++20 for these tests now, and
removing the hardcoded -std option allows them to be tested for C++23
and C++26 as well.

libstdc++-v3/ChangeLog:

	* testsuite/std/concepts/1.cc: Remove dg-options.
	* testsuite/std/concepts/2.cc: Likewise.
	* testsuite/std/concepts/concepts.callable/invocable.cc:
	Likewise.
	* testsuite/std/concepts/concepts.callable/regular_invocable.cc:
	Likewise.
	* testsuite/std/concepts/concepts.callable/relation.cc:
	Likewise.
	* testsuite/std/concepts/concepts.callable/strictweakorder.cc:
	Likewise.
	* testsuite/std/concepts/concepts.lang/concept.arithmetic/floating_point.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.arithmetic/integral.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.arithmetic/signed_integral.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.arithmetic/unsigned_integral.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.assignable/1.cc:
	Likewise.
	* testsuite/std/concepts/concepts.lang/concept.common/1.cc:
	Likewise.
	* testsuite/std/concepts/concepts.lang/concept.commonref/1.cc:
	Likewise.
	* testsuite/std/concepts/concepts.lang/concept.constructible/1.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.convertible/1.cc:
	Likewise.
	* testsuite/std/concepts/concepts.lang/concept.copyconstructible/1.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.defaultinitializable/1.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.defaultinitializable/lwg3149.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.derived/1.cc:
	Likewise.
	* testsuite/std/concepts/concepts.lang/concept.destructible/1.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.moveconstructible/1.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.same/1.cc:
	Likewise.
	* testsuite/std/concepts/concepts.lang/concept.swappable/swap.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.swappable/swappable.cc: Likewise.
	* testsuite/std/concepts/concepts.lang/concept.swappable/swappable_with.cc: Likewise.
	* testsuite/std/concepts/concepts.object/copyable.cc: Likewise.
	* testsuite/std/concepts/concepts.object/movable.cc: Likewise.
	* testsuite/std/concepts/concepts.object/regular.cc: Likewise.
	* testsuite/std/concepts/concepts.object/semiregular.cc:
	Likewise.
	* testsuite/std/ranges/97600.cc: Likewise.
	* testsuite/std/ranges/access/101782.cc: Likewise.
	* testsuite/std/ranges/access/begin.cc: Likewise.
	* testsuite/std/ranges/access/begin_neg.cc: Likewise.
	* testsuite/std/ranges/access/cbegin.cc: Likewise.
	* testsuite/std/ranges/access/cdata.cc: Likewise.
	* testsuite/std/ranges/access/cend.cc: Likewise.
	* testsuite/std/ranges/access/crbegin.cc: Likewise.
	* testsuite/std/ranges/access/crend.cc: Likewise.
	* testsuite/std/ranges/access/data.cc: Likewise.
	* testsuite/std/ranges/access/empty.cc: Likewise.
	* testsuite/std/ranges/access/end.cc: Likewise.
	* testsuite/std/ranges/access/end_neg.cc: Likewise.
	* testsuite/std/ranges/access/lwg3467.cc: Likewise.
	* testsuite/std/ranges/access/p2602.cc: Likewise.
	* testsuite/std/ranges/access/rbegin.cc: Likewise.
	* testsuite/std/ranges/access/rend.cc: Likewise.
	* testsuite/std/ranges/access/size.cc: Likewise.
	* testsuite/std/ranges/access/size_neg.cc: Likewise.
	* testsuite/std/ranges/access/ssize.cc: Likewise.
	* testsuite/std/ranges/adaptors/100479.cc: Likewise.
	* testsuite/std/ranges/adaptors/100577.cc: Likewise.
	* testsuite/std/ranges/adaptors/93978.cc: Likewise.
	* testsuite/std/ranges/adaptors/95322.cc: Likewise.
	* testsuite/std/ranges/adaptors/99433.cc: Likewise.
	* testsuite/std/ranges/adaptors/all.cc: Likewise.
	* testsuite/std/ranges/adaptors/common.cc: Likewise.
	* testsuite/std/ranges/adaptors/conditionally_borrowed.cc:
	Likewise.
	* testsuite/std/ranges/adaptors/counted.cc: Likewise.
	* testsuite/std/ranges/adaptors/detail/copyable_box.cc:
	Likewise.
	* testsuite/std/ranges/adaptors/drop.cc: Likewise.
	* testsuite/std/ranges/adaptors/drop_while.cc: Likewise.
	* testsuite/std/ranges/adaptors/elements.cc: Likewise.
	* testsuite/std/ranges/adaptors/filter.cc: Likewise.
	* testsuite/std/ranges/adaptors/join.cc: Likewise.
	* testsuite/std/ranges/adaptors/lazy_split.cc: Likewise.
	* testsuite/std/ranges/adaptors/lazy_split_neg.cc: Likewise.
	* testsuite/std/ranges/adaptors/lwg3286.cc: Likewise.
	* testsuite/std/ranges/adaptors/lwg3313_neg.cc: Likewise.
	* testsuite/std/ranges/adaptors/lwg3325_neg.cc: Likewise.
	* testsuite/std/ranges/adaptors/lwg3406.cc: Likewise.
	* testsuite/std/ranges/adaptors/p1739.cc: Likewise.
	* testsuite/std/ranges/adaptors/p2281.cc: Likewise.
	* testsuite/std/ranges/adaptors/p2770r0.cc: Likewise.
	* testsuite/std/ranges/adaptors/reverse.cc: Likewise.
	* testsuite/std/ranges/adaptors/sizeof.cc: Likewise.
	* testsuite/std/ranges/adaptors/split.cc: Likewise.
	* testsuite/std/ranges/adaptors/take.cc: Likewise.
	* testsuite/std/ranges/adaptors/take_while.cc: Likewise.
	* testsuite/std/ranges/adaptors/transform.cc: Likewise.
	* testsuite/std/ranges/empty_view.cc: Likewise.
	* testsuite/std/ranges/headers/ranges/synopsis.cc: Likewise.
	* testsuite/std/ranges/iota/difference_type.cc: Likewise.
	* testsuite/std/ranges/iota/iota_view.cc: Likewise.
	* testsuite/std/ranges/iota/iterator.cc: Likewise.
	* testsuite/std/ranges/iota/lwg3292_neg.cc: Likewise.
	* testsuite/std/ranges/iota/max_size_type.cc: Likewise.
	* testsuite/std/ranges/istream_view.cc: Likewise.
	* testsuite/std/ranges/p2259.cc: Likewise.
	* testsuite/std/ranges/p2325.cc: Likewise.
	* testsuite/std/ranges/p2367.cc: Likewise.
	* testsuite/std/ranges/range.cc: Likewise.
	* testsuite/std/ranges/refinements.cc: Likewise.
	* testsuite/std/ranges/safe_range.cc: Likewise.
	* testsuite/std/ranges/safe_range_types.cc: Likewise.
	* testsuite/std/ranges/single_view.cc: Likewise.
	* testsuite/std/ranges/sized.cc: Likewise.
	* testsuite/std/ranges/subrange/1.cc: Likewise.
	* testsuite/std/ranges/subrange/97512.cc: Likewise.
	* testsuite/std/ranges/subrange/constexpr.cc: Likewise.
	* testsuite/std/ranges/subrange/lwg3282_neg.cc: Likewise.
	* testsuite/std/ranges/subrange/lwg3286.cc: Likewise.
	* testsuite/std/ranges/subrange/lwg3433.cc: Likewise.
	* testsuite/std/ranges/subrange/sizeof.cc: Likewise.
	* testsuite/std/ranges/subrange/tuple_like.cc: Likewise.
	* testsuite/std/ranges/view.cc: Likewise.