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

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https://hg.mozilla.org/integration/gaia-central/rev/70f416f86685
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Merge pull request #14077 from mcav/pop3-chunks

Bug 939374 - [email] POP3: Take smaller sync bites to avoid OOM errors. r=asuth

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https://hg.mozilla.org/integration/gaia-central/rev/20f84b645ec8
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Bug 939374 - [email] POP3: Take smaller sync bites to avoid OOM errors. r=asuth

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https://hg.mozilla.org/integration/gaia-central/rev/0dd6fac28782
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Merge pull request #13983 from pivanov/bug-939226

Bug 939226 - [Action Icons - Clock] Remove shadows from action icons

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https://hg.mozilla.org/integration/gaia-central/rev/e2b0c841b2fd
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 939226 - [Action Icons - Clock] Remove shadows from action icons