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

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https://hg.mozilla.org/integration/gaia-central/rev/dc499c7b2946
Author: Zac <zcampbell@mozilla.com>
Desc: Revert "Bug 999355 - Wait for 'render' class on appWindow to denote Gaia startup r=bebe"

This reverts commit 2aee4c38dee335f06951ef4e17f22b2f2ed8bd18.
Bumping manifests a=b2g-bump