'gcc.dg/pr88870.c': don't 'dg-require-effective-target nonlocal_goto'

I confirm that back then, 'gcc.dg/pr88870.c' for nvptx failed due to
'sorry, unimplemented: target cannot support nonlocal goto', however at some
(indeterminate) point in time, that must've disappeared, and we now don't have
to 'dg-require-effective-target nonlocal_goto' anymore, and therefore get:

    [-UNSUPPORTED:-]{+PASS:+} gcc.dg/pr88870.c {+(test for excess errors)+}

(And, if ever necessary again, this nowadays probably should
'dg-require-effective-target exceptions' instead of 'nonlocal_goto'.)

	gcc/testsuite/
	* gcc.dg/pr88870.c: Don't 'dg-require-effective-target nonlocal_goto'.