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/5b6b7b811174
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Revert "Uplift bug 912010, 928281 and 931977"

This reverts commit cce2ba1312b9a1fa534f446a46981d7ce6ee38fe, reversing
changes made to 90d2ede90cb19a7d1986950012b15c7024022205.