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/9274d1e6c588
Author: James Lal <james@lightsofapollo.com>
Desc: Bug 930500 - Many builds error because they can't find a binary, Bug 935489 - mozilla-download should always display the downloaded URL

a=tests
Bump up mozilla-download version
(cherry picked from commit 5422c15cf6555f2b13a5195544a5bec1dc09ca85)

Conflicts:
	package.json