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

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https://hg.mozilla.org/integration/gaia-central/rev/78e4bc24899e
Author: Francisco Jordano <fjordano@mozilla.com>
Desc: Bug 1042116 - Add bookmarks provide r=kgrandon r=daleharvey
Bumping manifests a=b2g-bump