[foozzie] Reduce probability of some extra flags

Mostly gc-related flags didn't flush out any bugs yet, but often reduce
test performance and lead to timeouts.

No-Try: true
Bug: chromium:1044942
Change-Id: I2a7b55f78bfa3d597de1a5674658829e0812d01a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2273861Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68608}

tools/clusterfuzz/v8_fuzz_flags.json

 [
-  [0.1, "--stress-marking=100"],
-  [0.1, "--stress-scavenge=100"],
-  [0.1, "--stress-compaction-random"],
-  [0.1, "--random-gc-interval=2000"],
+  [0.05, "--stress-compaction-random"],
+  [0.05, "--stress-delay-tasks"],
+  [0.05, "--stress-marking=100"],
+  [0.05, "--stress-scavenge=100"],
+  [0.05, "--random-gc-interval=2000"],
   [0.2, "--noanalyze-environment-liveness"],
-  [0.1, "--stress-delay-tasks"],
   [0.01, "--thread-pool-size=1"],
   [0.01, "--thread-pool-size=2"],
   [0.01, "--thread-pool-size=4"],