Bumping gaia.json for 2 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/589b71c66793
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #12388 from Seinlin/myanmar-kb

Bug 914572 - add a keyboard layout for Myanmar language, r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/a48b3b6a37c4
Author: Kai-Zhen Li <kli@mozilla.com>
Desc: Bug 914572 - add a keyboard layout for Myanmar language.