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

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https://hg.mozilla.org/integration/gaia-central/rev/ca9560e00377
Author: crdlc <crdlc@tid.es>
Desc: Bug 1020951 - [vertical] Activity cancelled prompt on vertical homescreen r=kgrandon
Bumping manifests a=b2g-bump