Bumping gaia.json for 4 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/6cd43ff6a22f
Author: Sam Joch <samuel@guiora.com>
Desc: Merge pull request #12351 from pivanov/bug-917830

Bug 917830 - [FM Radio] Use Full Line Highlights r=samjoch

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https://hg.mozilla.org/integration/gaia-central/rev/655dab896c2b
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 917830 - [FM Radio] Use Full Line Highlights

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https://hg.mozilla.org/integration/gaia-central/rev/cb2b1b5c0c2d
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #12606 from gasolin/issue-913895percent

Bug 913895 - [Flatfish][homescreen] better tablet swipe threadshold, r=crdlc

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https://hg.mozilla.org/integration/gaia-central/rev/fc0fac392926
Author: gasolin <gasolin@gmail.com>
Desc: Bug 913895 - [Flatfish][homescreen] better tablet swipe threadshold