Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/73442e5ccb1e
Author: Dave Hunt <dave.hunt@gmail.com>
Desc: Bug 1049723 - Post logs to Treeherder report. r=rwood r=jlal

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https://hg.mozilla.org/integration/gaia-central/rev/9caeaa8e5443
Author: Dave Hunt <dave.hunt@gmail.com>
Desc: Bug 1049723 - Exclude the artifact path from the link in Treeherder. r=rwood

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https://hg.mozilla.org/integration/gaia-central/rev/1b52998366d8
Author: Dave Hunt <dave.hunt@gmail.com>
Desc: Bug 1049723 - Replaced Treeherder command line options with environment variables. r=rwood
Bumping manifests a=b2g-bump