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

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https://hg.mozilla.org/integration/gaia-central/rev/aff973323f60
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 1004400 - Increase timeout in test_browser_play_youtube a=testonly r=me
Bumping manifests a=b2g-bump