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

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https://hg.mozilla.org/integration/gaia-central/rev/666d79c88fe6
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Merge pull request #26498 from eeejay/bug-1068967

Bug 1068967 - Make thumbnails accessible. r=punamdahiya

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https://hg.mozilla.org/integration/gaia-central/rev/0c72947f5394
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 1068967 - Make thumbnails accessible.
Bumping manifests a=b2g-bump