Bumping gaia.json for 3 gaia-central revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/2fa554a9d4ab
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #14728 from etiennesegonzac/bug-947863-basic-dialer-marionette-js

Bug 947863 - Sanity marionette JS integration tests for the Dialer r=ferjm

========

https://hg.mozilla.org/integration/gaia-central/rev/389f42e62170
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 947863 - Sanity marionette JS integration tests for the Dialer
(keypad and tab navigation)

========

https://hg.mozilla.org/integration/gaia-central/rev/d855b1859bca
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Revert "Bug 951570 - Disable persona tests they failing because of http://personatestuser.org/"

This reverts commit 04af8c92f3539454135fb59f5cc85f6a3fb4b64a.