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

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https://hg.mozilla.org/integration/gaia-central/rev/4c3121fffef0
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #12425 from dwi2/bug919891

Bug 919891 - [B2G] [Settings] Hint screen was blocked by Bluetooth pinco...r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/eedfc25b50c9
Author: tzhuang <tzhuang@mozilla.com>
Desc: Bug 919891 - [B2G] [Settings] Hint screen was blocked by Bluetooth pincode request