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

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https://hg.mozilla.org/integration/gaia-central/rev/8424befd2d59
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #12851 from crh0716/919868

Bug 919868 - Update connection status after got paired devices r=evelyn

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https://hg.mozilla.org/integration/gaia-central/rev/a38124de35ad
Author: Arthur Chen <crh0716@gmail.com>
Desc: Bug 919868 - Update connection status after got paired devices