Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/e4e6b26b2372
Author: Jan Jongboom <janjongboom@gmail.com>
Desc: Merge pull request #15857 from comoyo/bug964216

Bug 964216 - Use build_stage to build keyboard app. r=janjongboom

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https://hg.mozilla.org/integration/gaia-central/rev/0f18b5a2677d
Author: Jan Jongboom <janjongboom@gmail.com>
Desc: Bug 964216 - Use build_stage to build keyboard app

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https://hg.mozilla.org/integration/gaia-central/rev/76adca4a65ad
Author: Dale Harvey <dale@arandomurl.com>
Desc: Bug 964476 - Use seperate field to store favicon data. r=kgrandon
Bumping manifests a=b2g-bump