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

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https://hg.mozilla.org/integration/gaia-central/rev/73eea1a82139
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #17396 from svic/Bug_974725

Bug_974725: [B2G][NFC] Support different vcard mime types for Contacts

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https://hg.mozilla.org/integration/gaia-central/rev/21900f321a75
Author: Garner Lee <garner.lee@telekom.com>
Desc: Bug 974725: [B2G][NFC] Support different vcard mime types for Contacts r=alive
Bumping manifests a=b2g-bump