testsuite, rs6000: Remove all powerpc-*paired* uses

Similar to r15-710-g458b23bc8b3e2b which removed all uses of
powerpc-*-linux*paired*, this patch is to remove the remaining
powerpc-*paired* uses which I missed to catch with "*linux*"
in search keyword.

gcc/testsuite/ChangeLog:

	* lib/target-supports.exp (check_vect_support_and_set_flags): Remove
	the if arm checking powerpc-*paired*.
	(check_750cl_hw_available): Remove.
	(check_effective_target_vect_unpack): Remove the check on
	powerpc-*paired*.