Bumping gaia.json for 2 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/e7b7f2cfa6ca
Author: AndreiH <andrei.hutusoru@gmail.com>
Desc: Merge pull request #14261 from bobsilverberg/pr14027

Bug 921514 - Create app object for the Music app

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https://hg.mozilla.org/integration/gaia-1_2/rev/5884f137dc6b
Author: Sasha Kruglov <sashakruglov@hotmail.com>
Desc: migrate music app tests to app object