Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/51b4fd78db4b
Author: Min-Zhong "John" Lu <jlu@mozilla.com>
Desc: Merge pull request #23399 from mnjul/bug_942309_email_url_keep_same_layout

Bug 942309 - [keyboard] keyboard layout language changes for input type=url and type=email. r=rudyl. ui-r=ofeng

========

https://hg.mozilla.org/integration/gaia-central/rev/e28ee3f8e4c3
Author: John Lu [:mnjul] <jlu@mozilla.com>
Desc: Bug 942309 - [keyboard] keyboard layout language changes for input type=url and type=email
Bumping manifests a=b2g-bump