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

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https://hg.mozilla.org/integration/gaia-central/rev/a824661b8338
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #13146 from caiolima/bug_815093

Bug 815093 - Compose "new" activities are unable to return to calling app once message is sent

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https://hg.mozilla.org/integration/gaia-central/rev/8829732fae72
Author: Caio Lima <ticaiolima@gmail.com>
Desc: Bug 815093 - Compose activities returning to caller app r=julien