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

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https://hg.mozilla.org/integration/gaia-central/rev/9aab6bf3a530
Author: Amir Nissim <amirnissim@gmail.com>
Desc: Merge pull request #12956 from EverythingMe/925970-round-bgimage-dim

Bug 928717 - [e.me] Background image missing in HD devices

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https://hg.mozilla.org/integration/gaia-central/rev/825425a519f8
Author: Amir Nissim <amirn@everything.me>
Desc: Bug 928717 - [e.me] Background image missing in HD devices