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

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https://hg.mozilla.org/integration/gaia-central/rev/19756fa13aa0
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1007147 - [Home2] Follow-up, add overflow: hidden to icons to prevent x-axis panning r=me
Bumping manifests a=b2g-bump