Bumping gaia.json for 2 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/b5d66bc31278
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Merge pull request #12281 from eeejay/bug-916231

Bug 916231 - Add screen reader toggle to developer options. r=kaze

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https://hg.mozilla.org/integration/gaia-central/rev/706499ea0abd
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 916231 - Add screen reader toggle to developer options.