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

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https://hg.mozilla.org/integration/gaia-central/rev/ff4c36016726
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #12510 from KevinGrandon/bug_921531_use_platform_touch_events

Bug 921531 - Use platform touch events r=paul

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https://hg.mozilla.org/integration/gaia-central/rev/aced3038d2f0
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 921531 - Use platform touch events