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

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https://hg.mozilla.org/integration/gaia-central/rev/c9f88878f616
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Merge pull request #12458 from eeejay/bug-920796

Bug 920796 - Add menu roles to sleep menu. r=vingtetun

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https://hg.mozilla.org/integration/gaia-central/rev/5f9ff6d7dd34
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 920796 - Add menu roles to sleep menu