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

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https://hg.mozilla.org/integration/gaia-central/rev/e091dab8b696
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #13118 from cctuan/928254-2

Bug 928254 - [Flatfish][Gallery] support 2 column layout for tablet

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https://hg.mozilla.org/integration/gaia-central/rev/10d972474dd9
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 928254 - [Flatfish][Gallery] support 2 column layout for tablet