Disable flaky GSStoreTest

BUG=skia:6048

Change-Id: I86abfc0059c6523db08e552df16e88ae71379ed7
Reviewed-on: https://skia-review.googlesource.com/5733
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Eric Boren <borenet@google.com>
tree: e8604bbe4f17137f2d314043625d90e42c5d7323
  1. recipe_modules/
  2. recipes.py
  3. recipes/