Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/3b71d19cf8ba
Author: Jim Porter <jporter@mozilla.com>
Desc: Merge pull request #20839 from jimporter/ringtones-create-cancel

Bug 1028489 - [ringtones] Cancelling out of creating a ringtone (from the ma...

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https://hg.mozilla.org/integration/gaia-central/rev/e3e70cd005da
Author: Jim Porter <jporter@mozilla.com>
Desc: Bug 1028489 - [ringtones] Cancelling out of creating a ringtone (from the manager) doesn't clear events properly
Bumping manifests a=b2g-bump