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

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https://hg.mozilla.org/integration/gaia-central/rev/2f1b19a8190e
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #15163 from millermedeiros/951423-header-truncated

Bug 951423 - [B2G][Calendar][Day View]Header displays truncated if date exceeds eighteen characters.

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https://hg.mozilla.org/integration/gaia-central/rev/4b5b702f953f
Author: millermedeiros <miller@millermedeiros.com>
Desc: Bug 951423 - [B2G][Calendar][Day View]Header displays truncated if date exceeds eighteen characters.