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/19d8ad4f4185
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #12016 from gasolin/issue-911668

Bug 911668 - [homescreen] change build-in apps orientation to default, r=timdream
(cherry picked from commit 18c2ab4b7b2d4cacee90fb85e97354142b2fad4a)