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/4f66ff773ab9
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #13700 from Pike/bug-938052-keyboard-js-errors

bug 938052, better report js errors in keyboard layouts, and fix a few, r=djf, rudyl, yuren(cherry picked from commit 42a20aee4866b67d1adb83a96a826040ed5b2c48)