Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/b257ecce75f9
Author: Ed Morley <emorley@mozilla.com>
Desc: Revert "Bug 1047168 - Change test_browser_play_youtube_video.py to run local content and embedded video" for test failures

This reverts commit 627df3fa98b6721f823fb712321e8010c194f16f.
Bumping manifests a=b2g-bump