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

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https://hg.mozilla.org/integration/gaia-central/rev/df6096d1c2bd
Author: Florin Strugariu <bebef_1987@yahoo.com>
Desc: Merge pull request #15080 from zacc/bug_957163

Bug 957163 - Improve waits in the Keyboard app object when switching bet...

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https://hg.mozilla.org/integration/gaia-central/rev/1fa96bbaf9f9
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 957163 - Improve waits in the Keyboard app object when switching between layouts, after taps, improve comment/docs