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

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https://hg.mozilla.org/integration/gaia-central/rev/4fdb8cb1444e
Author: Sam Joch <samuel@guiora.com>
Desc: Merge pull request #11556 from pivanov/bug-903356

Bug 903356 - [FM Radio][HD] Center favorite radio station r=samjoch

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https://hg.mozilla.org/integration/gaia-central/rev/f5c43b34f270
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 903356 - [FM Radio][HD] Center favorite radio station