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/4172c62b7694
Author: Albert <acperez@tid.es>
Desc: Merge pull request #13515 from acperez/bug-936028

Bug 936028 - Remove appcache in hosted single variant apps to avoid wrong installation without internet connection. r=yurenju
(cherry picked from commit 82bc08983e78b4181f8c6297d01349873db30c79)