Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/373b6bd197c6
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #21157 from alivedise/bugzilla/1024483/immediate-homescreen-transition-on-firstboot

Bug 1024483 - Use immediate transition for homescreen from lockscreen, r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/b76c00250da3
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 1024483 - Use immediate transition for homescreen from lockscreen

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https://hg.mozilla.org/integration/gaia-central/rev/85ba44c525a7
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Revert "Bug 1029542 - Work around bug 1029542 so we can see collection bg image as we scroll"
Bumping manifests a=b2g-bump