Bumping gaia.json for 1 gaia-1_3 revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-1_3/rev/31994d318df7
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #14810 from etiennesegonzac/bug-946316-mochitest

Bug 946316 - Adding data store access to the mochitest app. r=etienne