PR libstdc++/95915
	* include/std/variant (_Uninitialized):
	Adjust the condition and the comment.
	* testsuite/20_util/variant/95915.cc: New.
	* testsuite/20_util/variant/compile.cc: Add new test.

(cherry picked from commit 24b54628cfa95194a8de4071c28cb56e6e81c08e)