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

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https://hg.mozilla.org/integration/gaia-central/rev/6c8f3580df38
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #24017 from yzen/bug-1066639

Bug 1066639 - fixed a cards view regression that caused it to be inacces...

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https://hg.mozilla.org/integration/gaia-central/rev/9b3cfcd6a28e
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 1066639 - fixed a cards view regression that caused it to be inaccessible. Added UI tests. r=alive
Bumping manifests a=b2g-bump