[omp, ftracer] Remove incorrect suggestion in ignore_bb_p

[omp, ftracer] Remove incorrect suggestion in ignore_bb_p

In commit ab3f4b27abe "[omp, ftracer] Don't duplicate blocks in SIMT region" I
added a comment in ignore_bb_p suggesting a reordering of SIMT_VOTE_ANY and
SIMT_EXIT, which is not possible since VOTE_ANY may have data dependencies to
storage that is deallocated by SIMT_EXIT.

I've now opened a PR (PR97291) to describe the problem the reordering was
intended to fix.

Remove the incorrect suggestion.

gcc/ChangeLog:

2020-10-05  Tom de Vries  <tdevries@suse.de>

	* tracer.c (ignore_bb_p): Remove incorrect suggestion.