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

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https://hg.mozilla.org/integration/gaia-central/rev/6d51266ba118
Author: Ian Liu <iliu@mozilla.com>
Desc: Merge pull request #11977 from EragonJ/bug-910254

Bug 910254 - [Clock] Alarm info layout needs refinement, r=@ian-liu

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https://hg.mozilla.org/integration/gaia-central/rev/d914b92b56b3
Author: EragonJ <eragonj@eragonj.me>
Desc: Bug 910254 - [Clock] Alarm info layout needs refinement

  - add unit test
  - update alarm-item styles