[foozzie] Raise experiment percentage for gc fuzzing

NOTRY=true
TBR=hpayer@chromium.org

Bug: v8:7012
Change-Id: I4f1a2468ef60e383480f8ea04d069a43296b30b0
Reviewed-on: https://chromium-review.googlesource.com/866837Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50600}

tools/foozzie/v8_foozzie.py

@@ -79,9 +79,9 @@ CONFIGS = dict(
 # Additional flag experiments. List of tuples like
 # (<likelihood to use flags in [0,1)>, <flag>).
 ADDITIONAL_FLAGS = [
-  (0.05, '--stress-marking=100'),
-  (0.05, '--stress-scavenge=100'),
-  (0.05, '--stress-compaction-random'),
+  (0.1, '--stress-marking=100'),
+  (0.1, '--stress-scavenge=100'),
+  (0.1, '--stress-compaction-random'),
 ]
 
 # Timeout in seconds for one d8 run.