Bumping gaia.json for 1 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/91fe480f4545
Author: Adam Hyland <protonk@gmail.com>
Desc: Bug 909343 [Clock] Refactor Date Math Utilities r=jugglinmike

Refactor utils.js to provide methods for:

- Conversion to milliseconds from objects with duration values, e.g.
  {hours: 4, seconds: 12} (for any combination of hours, minutes,
  seconds, etc.
- Conversion from millisecond interval to object with duration values.