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

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https://hg.mozilla.org/integration/gaia-central/rev/b8a669ee022f
Author: crdlc <crdlc@tid.es>
Desc: Bug 1020755 - (vertical-homescreen) Status bar should become 100% opaque when user scrolls r=alive r=kgrandon
Bumping manifests a=b2g-bump