libgomp: Fix comment typo

libgomp: Fix comment typo

I saw
FAIL: libgomp.fortran/target-nowait-array-section.f90   -O  execution test
in my last x86_64-linux bootstrap.  From quick skimming, it might be just
unreliable test, which assumes that asynchronous execution wouldn't produce
ordered sequence, but can't it happen even with asynchronous execution?

That said, while skimming the test, I've noticed a comment typo and
this patch fixes that up.

2023-02-16  Jakub Jelinek  <jakub@redhat.com>

	* testsuite/libgomp.fortran/target-nowait-array-section.f90: Fix
	comment typo and improve its wording.