Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/6c5e5eb05f88
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #18364 from timdream/lol-keyboard

Bug 997100 - Update test-keyboard-app, r=rudyl

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https://hg.mozilla.org/integration/gaia-central/rev/278e89db5398
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 997100 - Update test-keyboard-app

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https://hg.mozilla.org/integration/gaia-central/rev/ad77c74ee5aa
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #18192 from Moz-TedC/bug981938-redux

Bug 981938: Remove INDEX_ID entry. Instead, use sync() to fetch keys from the DataStore and store them in a list in an IndexedDB. r=arthurcc

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https://hg.mozilla.org/integration/gaia-central/rev/87e59df20317
Author: Ted Clancy (:tedders1) <tclancy@mozilla.com>
Desc: Bug 981938: Remove INDEX_ID entry. Instead, use sync() to fetch keys from the DataStore and store them in a list in an IndexedDB. r=arthurcc
Bumping manifests a=b2g-bump