Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/3868363f8d5e
Author: Dietrich Ayala <autonome@gmail.com>
Desc: Bug 960813 - [B2G][Browser][RTSP] Unable to add RTSP bookmark to the "Home screen" r=dale
Bumping manifests a=b2g-bump