Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-2_0/rev/47eabf570361
Author: Andrew Sutherland <asutherland@asutherland.org>
Desc: Bug 1058900 - [email] Workaround graphics corruption / memory spikes by cleaning up HTML display logic. r=jrburke

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https://hg.mozilla.org/integration/gaia-2_0/rev/bbb906dd1967
Author: Ryan VanderMeulen <ryanvm@gmail.com>
Desc: Merge pull request #24337 from julienw/1052447-v2.0-fix-exit-activity-on-delete

Bug 1052447 - [Messages] when we're in an activity and we delete all mes...

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https://hg.mozilla.org/integration/gaia-2_0/rev/f2d35f7af6fb
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 1052447 - [Messages] when we're in an activity and we delete all messages in the thread, we should close the activity r=azasypkin

Conflicts:
	apps/sms/js/thread_ui.js
Bumping manifests a=b2g-bump