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

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https://hg.mozilla.org/integration/gaia-central/rev/aef5e6f3cb6b
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #16099 from jrburke/bug969609-email-notification-black-screen

Bug 969609 - [B2G][Email]Opening an email notification then pressing back in the email app leads to a black screen r=asuth

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https://hg.mozilla.org/integration/gaia-central/rev/839fac80ff35
Author: jrburke <jrburke@gmail.com>
Desc: Bug 969609 - [B2G][Email]Opening an email notification then pressing back in the email app leads to a black screen.
Bumping manifests a=b2g-bump