libstdc++-v3/ChangeLog:

	LWG 3397 basic_istream_view::iterator should not provide
	iterator_category
	* include/std/ranges (basic_istream_view:_Iterator::iterator_category):
	Rename to ...
	(basic_istream_view:_Iterator::iterator_concept): ... this.
	* testsuite/std/ranges/istream_view.cc: Augment test.