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

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https://hg.mozilla.org/integration/gaia-central/rev/64a86fa375e9
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #14546 from karlt/943138

bug 943138 - improve dialer ADSR envelope r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/c8af3b692644
Author: Karl Tomlinson <karlt+@karlt.net>
Desc: bug 943138 - improve dialer ADSR envelope

Scheduling tones at AudioContext.currentTime resulted in the first part of the
tone being cut off, so start an AudioBufferSourceNode for the envelope.

Add a release phase for long dialer tones.

Revert the release period to 0.05 to match the prior mozWriteAudio
implementation.