'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'.

gcc/testsuite/gcc.dg/pr88870.c

@@ -1,6 +1,5 @@
 /* PR rtl-optimization/88870 */
 /* { dg-do compile } */
-/* { dg-require-effective-target nonlocal_goto } */
 /* { dg-options "-O1 -fexceptions -fnon-call-exceptions -ftrapv -fno-tree-dominator-opts" } */
 
 int a, b;