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

========

https://hg.mozilla.org/integration/gaia-central/rev/c7c750d66279
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #12680 from timdream/bug923788

Bug 923788 - Calculate position of lock screen icons based with calc() from center, r=gweng

========

https://hg.mozilla.org/integration/gaia-central/rev/4fb51c9b02ec
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 923788 - Calculate position of lock screen icons based with calc() from center