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

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https://hg.mozilla.org/integration/gaia-central/rev/3a8e94b5697c
Author: Dave Hunt <dave.hunt@gmail.com>
Desc: Bug 1049730 - Add XML and HTML reports to Treeherder as artifacts. r=mdas
Bumping manifests a=b2g-bump