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

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https://hg.mozilla.org/integration/gaia-central/rev/c4813215e307
Author: Mihai Cîrlănaru <mihai@cirlanaru.com>
Desc: Merge pull request #12683 from mcirlanaru/bug_911001

Bug 911001 - Don't reset power save mode when battery almost empty. r=@alivedise

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https://hg.mozilla.org/integration/gaia-central/rev/d5d519230d96
Author: Mihai Cirlanaru <mihai@cirlanaru.com>
Desc: Bug 911001 - Don't reset power save mode when battery almost empty. r=alive