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

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https://hg.mozilla.org/integration/gaia-central/rev/6469f3bd4b70
Author: Rex KM Lee <rexboy@mozilla.com>
Desc: Merge pull request #12846 from rexboy7/fix-bug917344

Bug 917344 - [Dialer] Turn off speaker if bluetooth headphone is connect...

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https://hg.mozilla.org/integration/gaia-central/rev/ca5994516df0
Author: Rex Lee <rexboy@mozilla.com>
Desc: Bug 917344 - [Dialer] Turn off speaker if bluetooth headphone is connected during a call