[test] Don't flush code for another flaky optimization test

Bug: v8:12329
Change-Id: I51c38d70537889b7534fb7e6b4066e6ab440234a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3248163
Auto-Submit: Shu-yu Guo <syg@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77582}

test/mjsunit/regress-1120905.js

@@ -4,6 +4,10 @@
 
 // Flags: --allow-natives-syntax
 
+// This test does not work well if we flush the feedback vector, which causes
+// deoptimization.
+// Flags: --no-stress-flush-code --no-flush-bytecode
+
 function O() {}
 O.prototype.f = f;
 O.prototype.g = g;