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

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https://hg.mozilla.org/integration/gaia-central/rev/283810a5962b
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #20954 from lightsofapollo/bug-1029542

Bug 1029542 - Work around bug 1029542 so we can see collection bg image ...

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https://hg.mozilla.org/integration/gaia-central/rev/8adfc1802128
Author: James Lal <james@lightsofapollo.com>
Desc: Bug 1029542 - Work around bug 1029542 so we can see collection bg image as we scroll
Bumping manifests a=b2g-bump