Bug 1054178 - [Gaia][calendar] support 24 hour time format

Fixed. [1][2]
[1] https://github.com/mozilla-b2g/gaia/pull/23063/files#diff-aebb1958df1b6b066d073763a38995e1R118
[2] https://github.com/mozilla-b2g/gaia/pull/23063/files#diff-6a15b36b79ca8afc7acf1ae4888a8ed4R29