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

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https://hg.mozilla.org/integration/gaia-central/rev/74bfb98d63ef
Author: steveck-chung <schung@mozilla.com>
Desc: Merge pull request #15073 from steveck-chung/message-information-page

Bug 949379 - [Gaia][Messages] Message report panel visual polish, r=julienw.

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https://hg.mozilla.org/integration/gaia-central/rev/49f4899741e9
Author: Steve Chung <schung@mozilla.com>
Desc: Bug 949379 - [Gaia][Messages] Message report panel visual polish