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

========

https://hg.mozilla.org/integration/gaia-1_2/rev/671ac6c3c9bc
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 939979 - Enable test_context_menu_picker.py r=me a=testonly