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

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https://hg.mozilla.org/integration/gaia-central/rev/6b1cdf59d132
Author: Mike Pennisi <mike@mikepennisi.com>
Desc: Bug 902999 - [Clock] Add Time To In-Progress Timer, "+1 Min"

https://bugzilla.mozilla.org/show_bug.cgi?id=902999

- Moves value accessor property to Picker.prototype
    - Defines set accessor operation for Picker.prototype.value
    - Defensive accessor handling

- Defines Timer.prototype.plus(seconds)
    - Add an arbitrary number of seconds to the current timer.
    - Seconds are auto-converted to milliseconds

- Tests for
    - Picker.prototype.value
    - Timer.prototype.plus()
    - Timer.prototype.commit()
Bumping manifests a=b2g-bump