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

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https://hg.mozilla.org/integration/gaia-1_2/rev/6fa8f7a12940
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #13867 from timdream/lockscreen-unlock-transition3

Bug 937630 - All you need is ... smooth unlock transition, r=vingtetun
(cherry picked from commit 45f65f707ae1d724c48c4ebf439d1617c35bbe42)

Conflicts:
	apps/system/js/lockscreen.js