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

========

https://hg.mozilla.org/integration/gaia-central/rev/f7d6e61b3516
Author: steveck-chung <schung@mozilla.com>
Desc: Merge pull request #14986 from steveck-chung/bug-947282

Bug 947282 - [Messaging] Bubbles style is not working properly with subject.  r= borjasalguero, a=status-b2g-v1.3 blocking

========

https://hg.mozilla.org/integration/gaia-central/rev/f9507c70f1c6
Author: Steve Chung <schung@mozilla.com>
Desc: Bug 947282 - [Messaging] Bubbles style is not working properly with subject