Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/f73bd4b45c4a
Author: Ben Kelly <bkelly@mozilla.com>
Desc: Merge pull request #17535 from wanderview/contacts-canvas-cleanup-2

Bug 983885: Aggressively cleanup img/canvas in contacts. r=jmcf

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https://hg.mozilla.org/integration/gaia-central/rev/c8f6151d9aad
Author: Ben Kelly <ben@wanderview.com>
Desc: Bug 983885: Aggressively cleanup img/canvas in contacts.
Bumping manifests a=b2g-bump