Reenable load:games:miniclip on Mac

I ran it locally, and it now seems to be having no problems

TBR=perezju@chromium.org

Bug: 664661
Change-Id: Ia8201db53d9687f4cc23736e29f3e45a1a2062fa
Reviewed-on: https://chromium-review.googlesource.com/544905Reviewed-by: Charlie Andrews <charliea@chromium.org>
Commit-Queue: Charlie Andrews <charliea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#481683}

tools/perf/page_sets/system_health/expectations.py

@@ -15,8 +15,6 @@ class SystemHealthDesktopCommonExpectations(expectations.StoryExpectations):
                       'crbug.com/712694')
     self.DisableStory('browse:tools:earth', [expectations.ALL],
                       'crbug.com/708590')
-    self.DisableStory('load:games:miniclip', [expectations.ALL_MAC],
-                      'crbug.com/664661')
     self.DisableStory('play:media:google_play_music', [expectations.ALL],
                       'crbug.com/649392')
     self.DisableStory('play:media:soundcloud', [expectations.ALL_WIN],