Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-2_1/rev/83476d9f2b3c
Author: Sam Foster <sam@sam-i-am.com>
Desc: Merge pull request #24852 from sfoster/exit-cards-state-bug-1067649

Bug 1067649 - v2.1 exit to app or homescreen. r=etienne

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https://hg.mozilla.org/integration/gaia-2_1/rev/6232dfe9158c
Author: Sam Foster <sfoster@mozilla.com>
Desc: Bug 1067649 - v2.1 exit to app or homescreen, fix UI cards-view test. r=etienne

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https://hg.mozilla.org/integration/gaia-2_1/rev/8faad7522b06
Author: Wil Clouser <clouserw@gmail.com>
Desc: Merge pull request #24727 from ngokevin/v2.1

new marketplace packages for v2.1 (bug 1067532) r=francisco

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https://hg.mozilla.org/integration/gaia-2_1/rev/a88b2b9c1e3b
Author: Kevin Ngo <ngoke@mozilla.com>
Desc: new marketplace packages for v2.1 (bug 1067532)
Bumping manifests a=b2g-bump