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

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https://hg.mozilla.org/integration/gaia-central/rev/3a486660af10
Author: vingtetun <21@vingtetun.org>
Desc: Merge pull request #21228 from vingtetun/bug1023794

Bug 1023794 - [Dialer][Call Screen] UI moved up when entering another ap...

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https://hg.mozilla.org/integration/gaia-central/rev/75ed1f5addb5
Author: Vivien Nicolas <vnicolas@mozilla.com>
Desc: Bug 1023794 - [Dialer][Call Screen] UI moved up when entering another apps and back to call screen. r=etienne
Bumping manifests a=b2g-bump