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

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https://hg.mozilla.org/integration/gaia-1_3/rev/2508e36d6e4c
Author: tzhuang <tzhuang@mozilla.com>
Desc: Bug 894744 - Use localStorage event to make inter-page communication between music app and music activity
Bumping manifests a=b2g-bump