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

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https://hg.mozilla.org/integration/gaia-central/rev/cc492bd8ccdf
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #13525 from etiennesegonzac/bug-936095-stack-manager-stay-background-apps

Bug 936095 - Adding "stayBackground" apps at the bottom of the stack. r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/9d125b80c4f4
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 936095 - Adding "stayBackground" apps at the bottom of the stack.
r=alive