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

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https://hg.mozilla.org/integration/gaia-central/rev/ec183496896f
Author: russnicoletti <rnicoletti@mozilla.com>
Desc: Merge pull request #17721 from russnicoletti/bug987224

Bug 987224 - [B2G][Video]Unable to watch videos in video app after deleting two videos. r=johu

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https://hg.mozilla.org/integration/gaia-central/rev/4ad830e404f5
Author: Russ Nicoletti <rnicoletti@mozilla.com>
Desc: Bug 987224 - [B2G][Video]Unable to watch videos in video app after deleting two videos

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https://hg.mozilla.org/integration/gaia-central/rev/9fdba1b0d711
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Merge pull request #14545 from mcav/smtp-creds

 Bug 805501 - Support different username / password / credentials for SMTP server from IMAP server. r=asuth

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https://hg.mozilla.org/integration/gaia-central/rev/4a7b3adf0d22
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Bug 805501 - Support different username / password / credentials for SMTP server from IMAP server. r=asuth
Bumping manifests a=b2g-bump