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

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https://hg.mozilla.org/integration/gaia-central/rev/dc6887ff7c12
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #25975 from timdream/input-keyboard-helper-all

Bug 1094561 - InputAppList, r=mnjul

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https://hg.mozilla.org/integration/gaia-central/rev/d6c214932d9e
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 1094561 - Part III, Hook InputAppList to KeyboardHelper

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https://hg.mozilla.org/integration/gaia-central/rev/e5b4c119e8cd
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 1094561 - Part II, Implement InputAppList

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https://hg.mozilla.org/integration/gaia-central/rev/0fd62ff6d45f
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 1094561 - Part I, Make MockDOMRequest then-able
Bumping manifests a=b2g-bump