[test] Add more timeout to predictable testing

TBR=tmrts@chromium.org
NOTRY=true

Bug: v8:9145
Change-Id: Ica93b2c8dc9b90121802c6109c7e102435210e3d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1591607Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61211}

tools/testrunner/base_runner.py

@@ -722,7 +722,7 @@ class BaseTestRunner(object):
     if self.build_config.lite_mode:
       factor *= 2
     if self.build_config.predictable:
-      factor *= 2
+      factor *= 2.5
     if self.build_config.use_sanitizer:
       factor *= 1.5