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

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https://hg.mozilla.org/integration/gaia-central/rev/6f431b859346
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #13939 from flodolo/bug941901

Bug 941901 - [settings] Use correct entity name for Cell broadcast r=crh0716

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https://hg.mozilla.org/integration/gaia-central/rev/57b828b22513
Author: Francesco Lodolo (:flod) <flod@lodolo.net>
Desc: Bug 941901 - [settings] Use correct entity name for Cell broadcast

Mispelled data-l10n-id (callBroadcast instead of cellBroadcast)