libstdc++: Avoid CTAD for std::ranges::join_view [LWG 3474]

libstdc++: Avoid CTAD for std::ranges::join_view [LWG 3474]

In commit ef275d1f2083f8a1fa1b59a3cd07fd3e8431023e I implemented the
wrong resolution of LWG 3474. This removes the deduction guide and
alters the views::join factory to create the right type explicitly.

libstdc++-v3/ChangeLog:

	* include/std/ranges (join_view): Remove deduction guide.
	(views::join): Add explicit template argument list to prevent
	deducing the wrong type.
	* testsuite/std/ranges/adaptors/join.cc: Move test for LWG 3474
	here, from ...
	* testsuite/std/ranges/adaptors/join_lwg3474.cc: Removed.