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

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https://hg.mozilla.org/integration/gaia-central/rev/31c586470ff2
Author: Rudy Lu <left.lu@gmail.com>
Desc: Merge pull request #12779 from bmac/924846

Bug 924846 - [Keyboard][V1.2] Selected keyboard cannot be displayed whil...
r=gchen

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https://hg.mozilla.org/integration/gaia-central/rev/0603b7b9c2ba
Author: bmac <bmac325@GMail.com>
Desc: Bug 924846 - [Keyboard][V1.2] Selected keyboard cannot be displayed while switching the keyboard between built-in keyboard and third party keyboard