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

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https://hg.mozilla.org/integration/gaia-central/rev/ff8c83f97fe8
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1016748 - Disable accessibility test due to travis perma-fail
Bumping manifests a=b2g-bump