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

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https://hg.mozilla.org/integration/gaia-central/rev/6bddd383012e
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Merge pull request #16582 from mcav/perfmark

Bug 837670 - [Clock] "ready to use" perf measurement. r=jugglinmike

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https://hg.mozilla.org/integration/gaia-central/rev/687699b043d2
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Bug 837670 - [Clock] "ready to use" perf measurement. r=jugglinmike

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https://hg.mozilla.org/integration/gaia-central/rev/5b1b283beeb1
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Merge pull request #16630 from mcav/dumb-l10n-gmail

Bug 975654 - [B2G][l10n][Email] Disabling IMAP on a Gmail account expose...

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https://hg.mozilla.org/integration/gaia-central/rev/c9f9392bd474
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Bug 975654 - [B2G][l10n][Email] Disabling IMAP on a Gmail account exposes user to old UI which is globally not translated. r=asuth
Bumping manifests a=b2g-bump