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

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https://hg.mozilla.org/integration/gaia-central/rev/789d0a2d423b
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #20197 from KevinGrandon/bug_1022383_collection_columns

Bug 1022383 - [Collection App] Should show four columns instead of three

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https://hg.mozilla.org/integration/gaia-central/rev/2061a10e8d9a
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1022383 - [Collection App] Should show four columns instead of three r=amirn
Bumping manifests a=b2g-bump