testsuite: fix proc unsupported overriding in modules.exp [PR108899]

testsuite: fix proc unsupported overriding in modules.exp [PR108899]

The overrider of proc unsupported in modules.exp had two problems
reported by Thomas Schwinge, even after Jakub Jelínek's fix:

- it remained in effect while running other dejagnu testsets

- it didn't quote correctly the argument list passed to it, which
  caused test names to be surrounded by curly braces, as in:

UNSUPPORTED: {...}

This patch fixes both issues, obsoleting and reverting Jakub's change,
by dropping the overrider and renaming the saved proc back, and by
using uplevel's argument list splicing.

Co-authored-by: Thomas Schwinge <thomas@codesourcery.com>
for  gcc/testsuite/ChangeLog

	PR testsuite/108899
	* g++.dg/modules/modules.exp (unsupported): Drop renaming.
	Fix quoting.