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

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https://hg.mozilla.org/integration/gaia-central/rev/9390a2bb8915
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #13060 from flodolo/typo_costcontrol

Bug 930417 - (Cost Control) Typo in short name for December

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https://hg.mozilla.org/integration/gaia-central/rev/4ec4a555a8ac
Author: Francesco Lodolo (:flod) <flod@lodolo.net>
Desc: Bug 930417 - (Cost Control) Typo in short name for December

Should be DEC, not DEV. Affecting also 1.2