[heap] Bail out of test that doesn't support --noflush-code

... when we run without code flushing.

BUG=

Change-Id: I956c53732598d805581388453010238c029fc3ba
Reviewed-on: https://chromium-review.googlesource.com/458199Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44016}

test/cctest/heap/test-heap.cc

@@ -3873,6 +3873,7 @@ TEST(Regress165495) {
 
 TEST(Regress169209) {
   if (!i::FLAG_incremental_marking) return;
+  if (!i::FLAG_flush_code) return;
   i::FLAG_always_opt = false;
   i::FLAG_stress_compaction = false;
   i::FLAG_allow_natives_syntax = true;