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

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https://hg.mozilla.org/integration/gaia-central/rev/74d7c4e578b1
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #24885 from pivanov/bug-1078174

Bug 1078174 - [Contact] Improve UI on contact settings

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https://hg.mozilla.org/integration/gaia-central/rev/2e6aca22423c
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 1078174 - [Contact] Improve UI on contact settings
Bumping manifests a=b2g-bump