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

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https://hg.mozilla.org/integration/gaia-central/rev/90567ec7746a
Author: steveck-chung <schung@mozilla.com>
Desc: Merge pull request #14343 from steveck-chung/bug-929317

Bug 929317 - [Message] Message waiting UI was flicked while start up. r=julienw

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https://hg.mozilla.org/integration/gaia-central/rev/f659f457c69c
Author: Steve Chung <schung@mozilla.com>
Desc: Bug 929317 - [Message] Message waiting UI was flicked while start up