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

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https://hg.mozilla.org/integration/gaia-central/rev/ff786bb85ec6
Author: Dave Hunt <dave.hunt@gmail.com>
Desc: Revert "resend pr for bug 948826"

This reverts commit 0214caef6fd00eb5ae5f439d911766ba4c15ed2d.
Bumping manifests a=b2g-bump