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

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https://hg.mozilla.org/integration/gaia-central/rev/3a3d0bd683a4
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #26705 from huchengtw-moz/bug-1101371-visual-card-list

Bug 1101371 - [Stingray][home] apply visual spec to card list, r=rexboy

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https://hg.mozilla.org/integration/gaia-central/rev/31a3ec0cfa2d
Author: John Hu <johu@mozilla.com>
Desc: Bug 1101371 - [Stingray][home] apply visual spec to card list
Bumping manifests a=b2g-bump