libstdc++: testsuite: Reduce max_size_type.cc exec time [PR113175]

The adjustment to max_size_type.cc in r14-205-g83470a5cd4c3d2
inadvertently increased the execution time of this test by over 5x due
to making the two main loops actually run in the signed_p case instead
of being dead code.

To compensate, this patch cuts the relevant loops' range [-1000,1000] by
10x as proposed in the PR.  This shouldn't significantly weaken the test
since the same important edge cases are still checked in the smaller range
and/or elsewhere.  On my machine this reduces the test's execution time by
roughly 10x (and 1.6x relative to before r14-205).

	PR testsuite/113175

libstdc++-v3/ChangeLog:

	* testsuite/std/ranges/iota/max_size_type.cc (test02): Reduce
	'limit' to 100 from 1000 and adjust 'log2_limit' accordingly.
	(test03): Likewise.

(cherry picked from commit a138b996)