Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/8d9abe4b316a
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Merge pull request #25279 from eeejay/bug-1083944

Bug 1083944 -  Implement screen reader quick navigation dialog. r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/79a66c59793a
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 1083944 - Implement screen reader quick navigation dialog
Bumping manifests a=b2g-bump