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

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https://hg.mozilla.org/integration/gaia-central/rev/afb7475b9711
Author: crdlc <crdlc@tid.es>
Desc: Bug 1015000 - [Vertical Homescreen] Trying to stop a flywheel scrolling start an application r=kgrandon
Bumping manifests a=b2g-bump