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

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https://hg.mozilla.org/integration/gaia-central/rev/4262bf9de7fc
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Bug 1016885 - Always initialize the MmiManager before sending a notification r=etienne
Bumping manifests a=b2g-bump