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

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https://hg.mozilla.org/integration/gaia-central/rev/373ab3009a8a
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Merge pull request #12157 from dominickuo/bug-838008

Bug 838008 - [email] Enable picking video and audio files as attachment, r=@asutherland

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https://hg.mozilla.org/integration/gaia-central/rev/0dda4bce72b7
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Bug 838008 - [email] Enable picking video and audio files as attachment