Bumping gaia.json for 3 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/8aa52bb04742
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Merge pull request #13537 from eeejay/bug-920839

Bug 920839 - Make Value selectors accessible. r=timdream

Re-merged after fixing unit tests.

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https://hg.mozilla.org/integration/gaia-central/rev/6a7c649f88cc
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 920839 - Added spinbutton ARIA markup to value picker.

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https://hg.mozilla.org/integration/gaia-central/rev/94f157d99683
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 920839 - ARIA fixes to value selector.