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

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https://hg.mozilla.org/integration/gaia-central/rev/4adf821268c5
Author: vingtetun <21@vingtetun.org>
Desc: Merge pull request #12833 from vingtetun/warm.launch.repainted

Bug 926535 - Wait for the app to be fully repainted before starting the ...

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https://hg.mozilla.org/integration/gaia-central/rev/1cb5091d400b
Author: Vivien Nicolas <21@vingtetun.org>
Desc: Bug 926535 - Wait for the app to be fully repainted before starting the warm launch transition. r=alive