Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-1_4/rev/cbef38e06c3e
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #19492 from jrburke/bug1010867-email-slow-down-there-buddy

Bug 1010867 - [OPENC_1.3][email/UI] Message notification handling is pushing message_reader onto the stack twice r=asuth
Bumping manifests a=b2g-bump