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

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https://hg.mozilla.org/integration/gaia-central/rev/39f8b51560ab
Author: Aleh Zasypkin <aleh.zasypkin@gmail.com>
Desc: Merge pull request #21997 from azasypkin/bug-1041124-messages-manager-events

Bug 1041124 - [Messages][Refactoring] Make use of EventDispatcher in MessageManager. r=julien

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https://hg.mozilla.org/integration/gaia-central/rev/46ed5ddb4704
Author: Aleh Zasypkin <azasypkin@mozilla.com>
Desc: Bug 1041124 - [Messages][Refactoring] Make use of EventDispatcher in MessageManager. r=julien
Bumping manifests a=b2g-bump