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

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https://hg.mozilla.org/integration/gaia-central/rev/637b88e4d8ee
Author: Andrew Sutherland <asutherland@asutherland.org>
Desc: Merge pull request #11139 from asutherland/email-imap-fakeserver-fixes

Bug 813411 - [email/IMAP] port/import Thunderbird's IMAP and SMTP fake-servers. r=jrburke

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https://hg.mozilla.org/integration/gaia-central/rev/d3c573551c77
Author: Andrew Sutherland <asutherland@asutherland.org>
Desc: Bug 813411 - [email/IMAP] port/import Thunderbird's IMAP and SMTP fake-servers. r=jrburke

Land changes from https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/224