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

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https://hg.mozilla.org/integration/gaia-central/rev/c4297293a573
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #19109 from crdlc/avoid-overflow-vertical-home

Bug 1008144 - Avoid reflows in dragdrop r=kgrandon

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https://hg.mozilla.org/integration/gaia-central/rev/904a99b0a536
Author: crdlc <crdlc@tid.es>
Desc: Bug 1008144 - Avoid reflows in dragdrop
Bumping manifests a=b2g-bump