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

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https://hg.mozilla.org/integration/gaia-central/rev/48274490bc2d
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #11997 from caiolima/bug-905208

Bug 905208 - Implemented the banner when a new message of a thread arrive

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https://hg.mozilla.org/integration/gaia-central/rev/2e8a16ea5f35
Author: Caio Lima <ticaiolima@gmail.com>
Desc: Bug 905208 - Implemented the banner when a new message of a thread arrive r=julien