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

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https://hg.mozilla.org/integration/gaia-central/rev/a0aa928f3b25
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #16374 from etiennesegonzac/bug-972277-missing-statusbar-lockscreen

Bug 972277 - Making sure the statusbar is on the lockscreen when the active app is fullscreen. r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/cffc8c01295b
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 972277 - Making sure the statusbar is on the lockscreen when the active app is fullscreen.
r=timdream
Bumping manifests a=b2g-bump