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

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https://hg.mozilla.org/integration/gaia-central/rev/3ef8194476ef
Author: Gregor Wagner <anygregor@gmail.com>
Desc: Merge pull request #14738 from gregorwagner/back

Revert "Merge pull request #12717 from punamdahiya/Bug924170_Video_Mario...

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https://hg.mozilla.org/integration/gaia-central/rev/1f5915accd4f
Author: Gregor Wagner <anygregor@gmail.com>
Desc: Revert "Merge pull request #12717 from punamdahiya/Bug924170_Video_Marionette_Tests"

This reverts commit 7deffe21aedd0b1908d981be4a348f148a4332e8, reversing
changes made to 1f275beb53779feb31e1b00611c5e85428c431ae.