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

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https://hg.mozilla.org/integration/gaia-central/rev/51dc7b387943
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #12525 from paulrouget/turn-screen-on-on-debug-prompt

Bug 914557 - Turn on the screen (brightness, not unlock) when the connect prompt appears. r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/48d9752c2c24
Author: Paul Rouget <me@paulrouget.com>
Desc: Bug 914557 - Turn on the screen when the connect prompt appears. r=alive