Mark gcc.dg/shrink-wrap-loop.c as XFAIL.

Mark gcc.dg/shrink-wrap-loop.c as XFAIL.

It occurs to me that I should not have disabled early jump threading in
this test, as it may hide an actual defect.  I have reverted my change
and XFAILed the test instead.  I have also opened a PR101690 to keep track
of this problem.

gcc/testsuite/ChangeLog:

	* gcc.dg/shrink-wrap-loop.c: Enable early jump threading.  Mark as
	XFAIL.