Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/57b296e44333
Author: Amir Nissim <amirnissim@gmail.com>
Desc: Bug 1024387 - [Collection App] Basic background support for Collection icons r=ranbena
Bumping manifests a=b2g-bump