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

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https://hg.mozilla.org/integration/gaia-central/rev/191af2a6463e
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Merge pull request #14073 from zacc/bug_937336_homescreen

Bug 937336 - Remove explicit frame switching from Homescreen/everything ...

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https://hg.mozilla.org/integration/gaia-central/rev/2017c48f8a7b
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 937336 - Remove explicit frame switching from Homescreen/everything me app objects and tests