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

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https://hg.mozilla.org/integration/gaia-central/rev/765d194f0927
Author: russnicoletti <rnicoletti@mozilla.com>
Desc: Merge pull request #21134 from russnicoletti/bug-837676

Bug 837676 [video] Implement new startup loading events r=johu

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https://hg.mozilla.org/integration/gaia-central/rev/de4c492405be
Author: Russ Nicoletti <rnicoletti@mozilla.com>
Desc: Bug 837676 [video] Implement new startup loading events
Bumping manifests a=b2g-bump