Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/50826c9055cc
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #20709 from awiss/unread_msgs

Bug 800402 - [email] UI: Show the number of unread messages in the message-list header after the folder name r=jrburke

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https://hg.mozilla.org/integration/gaia-central/rev/04a0e0278ffd
Author: Alex Wissmann <awiss@mozilla.com>
Desc: Bug 800402 - [email] UI: Show the number of unread messages in the message-list header after the folder name
Bumping manifests a=b2g-bump