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

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https://hg.mozilla.org/integration/gaia-central/rev/c4feba5b3b58
Author: Sergi Mansilla <sergi.mansilla@gmail.com>
Desc: Merge pull request #20047 from sergi/browser_cleanup

Bug 1020723 - Remove NFC duplicated code [r=daleharvey]

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https://hg.mozilla.org/integration/gaia-central/rev/eb5ff2aa4f88
Author: Sergi Mansilla <sergi.mansilla@gmail.com>
Desc: Bug 1020723 - Remove NFC duplicated code
Bumping manifests a=b2g-bump