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

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https://hg.mozilla.org/integration/gaia-central/rev/d347cf2a6853
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #22324 from zacc/bug_1039966

Revert "Revert "Bug 1039966 - Update gaiatest marionette_client to 0.8.1...

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https://hg.mozilla.org/integration/gaia-central/rev/11876f8682d1
Author: Zac <zcampbell@mozilla.com>
Desc: Revert "Revert "Bug 1039966 - Update gaiatest marionette_client to 0.8.1 and dependency moztest to >= 0.6""

This reverts commit d15e133c0bac9f22218991ea2de157387ece792c.

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https://hg.mozilla.org/integration/gaia-central/rev/08a176cd64ea
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #22087 from yzen/bug-1042944

Bug 1042944 - added screen reader functionality to the system accessibil...

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https://hg.mozilla.org/integration/gaia-central/rev/771623fe5b16
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 1042944 - added screen reader functionality to the system accessibility component. r=alive
Bumping manifests a=b2g-bump