testsuite: Fix up PR108525 test [PR108525]

Seems when committing the PR108525 fix I've missed that a test with
the same name had been added a few hours before for PR108526.

This patch separates the PR108525 test into a new file.

2023-02-08  Jakub Jelinek  <jakub@redhat.com>

	PR c++/108525
	* g++.dg/cpp23/static-operator-call5.C: Move PR108525 testcase
	incorrectly applied into PR108526 testcase ...
	* g++.dg/cpp23/static-operator-call6.C: ... here.  New test.