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

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https://hg.mozilla.org/integration/gaia-central/rev/188cfaf15a1d
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #13477 from AndreiH/bug934446

Bug 934446 - Test Messages contact input validation

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https://hg.mozilla.org/integration/gaia-central/rev/3c8dd899322e
Author: Andrei Hutusoru <andreihutusoru@P5069.(none)>
Desc: Bug 934446 - Test Messages contact input validation