Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/dcb55fbcaa9b
Author: Jim Porter <jporter@mozilla.com>
Desc: Merge pull request #20642 from jimporter/ringtones-manage-activity

Bug 1024779 - [ringtones] edge gestures doesn't work

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https://hg.mozilla.org/integration/gaia-central/rev/6360719e181d
Author: Jim Porter <jporter@mozilla.com>
Desc: Bug 1024779 - [ringtones] edge gestures doesn't work

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https://hg.mozilla.org/integration/gaia-central/rev/5e2194fbe2c1
Author: Jared Hirsch <ohai@6a68.net>
Desc: Merge pull request #20762 from 6a68/bug-1027487-fmd-server-update

Bug 1027487 - Point FMD Client to New Stage Server URLs

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https://hg.mozilla.org/integration/gaia-central/rev/e832d6a01c32
Author: Jared Hirsch <ohai@6a68.net>
Desc: Bug 1027487 - Point FMD Client to New Stage Server URLs
Bumping manifests a=b2g-bump