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

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https://hg.mozilla.org/integration/gaia-central/rev/3db9a6d567fe
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #21356 from jrburke/bug915643-email-clear-notifications

Bug 915643 - [Email] Clear old notifications once Notification.get is available r=asuth

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https://hg.mozilla.org/integration/gaia-central/rev/582e188f6fe4
Author: jrburke <jrburke@gmail.com>
Desc: Bug 915643 - [Email] Clear old notifications once Notification.get is available
Bumping manifests a=b2g-bump