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

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https://hg.mozilla.org/integration/gaia-central/rev/cfada1d1d3f4
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 1021767 - Remove switch_to_displayed_app from _set_pref/_get_pref for consistency. r=dhunt
Bumping manifests a=b2g-bump