Bumping gaia.json for 3 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/39ec2afa396d
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #13968 from timdream/keyboard-pref-off2-v1.2

Bug 941885 - (v1.2) Hide 3rd-party keyboard apps under a settings db entry, r=rudyl

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https://hg.mozilla.org/integration/gaia-1_2/rev/2d6c2947d7c3
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 941885 - (v1.2) Set pref to off

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https://hg.mozilla.org/integration/gaia-1_2/rev/69510fdefc75
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 941885 - Hide 3rd-party keyboard apps under a settings db entry