Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-2_0/rev/2f6668b227e6
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Revert "Bug 1029542 - Work around bug 1029542 so we can see collection bg image as we scroll"
Bumping manifests a=b2g-bump