Bumping gaia.json for 1 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/b945e470cf9f
Author: Ben Kelly <bkelly@mozilla.com>
Desc: Merge pull request #13925 from wanderview/contacts-group-overflow-3

Bug 937291: Limit overflow of each group list.  r=arcturus