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

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https://hg.mozilla.org/integration/gaia-central/rev/b6bb78aff2f3
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #19043 from KevinGrandon/bug_1007352_bookmark_into_last_group

Bug 1007281 - [Homescreen] bookmarking sites will place icon on its own row with a horizontal Row separating it

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https://hg.mozilla.org/integration/gaia-central/rev/f225a9f6bb42
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1007281 - [Homescreen] bookmarking sites will place icon on its own row with a horizontal Row separating it r=crdlc
Bumping manifests a=b2g-bump