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

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https://hg.mozilla.org/integration/gaia-central/rev/a3e7f7a776f0
Author: Justin D'Arcangelo <justindarc@gmail.com>
Desc: Merge pull request #17955 from justindarc/bug991813

Bug 991813 - [Camera] Zoom Bar jumps on orientation change

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https://hg.mozilla.org/integration/gaia-central/rev/3a838b9a99db
Author: Justin D'Arcangelo <justindarc@gmail.com>
Desc: Bug 991813 - [Camera] Zoom Bar jumps on orientation change
Bumping manifests a=b2g-bump