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

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https://hg.mozilla.org/integration/gaia-central/rev/85c3d3ec06cc
Author: Fabien Cazenave <fabien@mozilla.com>
Desc: Merge pull request #16247 from fabi1cazenave/smsUpdateThread-bug968815

Bug 968815 - [SMS] update thread when last message is deleted, r=julienw

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https://hg.mozilla.org/integration/gaia-central/rev/31024440c700
Author: Fabien Cazenave <fabien@cazenave.cc>
Desc: Bug 968815 - [SMS] update thread when last message is deleted, r=julienw
Bumping manifests a=b2g-bump