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

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https://hg.mozilla.org/integration/gaia-central/rev/a4e31429c4de
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #20287 from timdream/keyboard-lazily-l10n2

Bug 1013207 - [Keyboard][Performance] Lazily load l10n.js, r=rudyl

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https://hg.mozilla.org/integration/gaia-central/rev/6a92c23b7caa
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 1013207 - [Keyboard][Performance] Lazily load l10n.js
Bumping manifests a=b2g-bump