Bumping gaia.json for 1 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/393b5209f9bc
Author: John Hu <johu@mozilla.com>
Desc: Bug 878735 - [SMS / MMS] entering new message screen not rendering correctly when accessed via contacts app - r=gnarf

Closes gh-10204