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

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https://hg.mozilla.org/integration/gaia-central/rev/b8cfc9be4a09
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Revert "Bug 938467 - gUM permission grant scenario - remember my choice support"

This reverts commit e46ca53452c5ef434112bf02abf1ea311ba22e9f.
Bumping manifests a=b2g-bump