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/ab0867b3d67c
Author: Malini Das <mdas@mozilla.com>
Desc: Bug 943008 - Enable pinning of marionette_client package in setup.py. r=dhunt