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

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https://hg.mozilla.org/integration/gaia-2_0/rev/9461e405fb69
Author: Sherman Chen <shamenchens@users.noreply.github.com>
Desc: Merge pull request #24333 from shamenchens/Bug1061401-MultipleActivityWindow-v20

Bug 1061401 - Fix multiple activity window orientation issue, r=alive

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https://hg.mozilla.org/integration/gaia-2_0/rev/83d876b800f8
Author: Sherman Chen <shamen.chens@gmail.com>
Desc: Bug 1061401 - Fix multiple activity window orientation issue
Bumping manifests a=b2g-bump