Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/8f2286ab3f8e
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1110630 - merge pull request #26774 from etiennesegonzac:bug-1110630 to mozilla-b2g:master

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https://hg.mozilla.org/integration/gaia-central/rev/8a0d978d4a94
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 1110630 - Hide overlays on sheetsgestureend even if the app is already active.
Bumping manifests a=b2g-bump