Remove xfail for hppa*-*-hpux* from stdatomic-flag.c and stdatomic-flag-2.c

Tests now pass on hppa64-hp-hpux11.11.

2024-01-16  John David Anglin  <danglin@gcc.gnu.org>

gcc/testsuite/ChangeLog:

	* gcc.dg/atomic/stdatomic-flag.c: Remove xfail.
	* gcc.dg/atomic/stdatomic-flag-2.c: Likewise.