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

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https://hg.mozilla.org/integration/gaia-central/rev/fd42316f0b7e
Author: Evyatar Amitay <evyatron@gmail.com>
Desc: Merge pull request #12605 from EverythingMe/922971-api-retries

[Bug 922971] Make sure retry number is finite and can be aborted [r=ranbena]

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https://hg.mozilla.org/integration/gaia-central/rev/8b0c354c56ad
Author: Evyatar Amitay <evyatron@gmail.com>
Desc: [Bug 922971] Make sure retry number is finite and can be aborted [r=ranbena]

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https://hg.mozilla.org/integration/gaia-central/rev/754f8abb6911
Author: Sam Joch <samuel@guiora.com>
Desc: Merge pull request #12352 from pivanov/bug-917826

Bug 917826 - [Clock] Use Full Line Highlights r=samjoch

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https://hg.mozilla.org/integration/gaia-central/rev/21373f508864
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 917826 - [Clock] Use Full Line Highlights