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

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https://hg.mozilla.org/integration/gaia-central/rev/5d2185eee255
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Merge pull request #12995 from mikehenrty/bug-926714-notification-tests

Bug 926714 - Follow up to 899574: add integration tests for Notification...

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https://hg.mozilla.org/integration/gaia-central/rev/13207b6cf374
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Bug 926714 - Follow up to 899574: add integration tests for Notification.Get()