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

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https://hg.mozilla.org/integration/gaia-central/rev/3628d253f568
Author: Zac <zcampbell@mozilla.com>
Desc: Revert "Revert "Bug 999355 - Wait for 'render' class on appWindow to denote Gaia startup r=bebe""

This reverts commit 94af5ce3f4e0ed455a10ce15c71d103b8403e43e.
Bumping manifests a=b2g-bump