Update fastify.listen usage to non-deprecated signature

[bsmilling]

Fixes #50

[coveralls]

Pull Request Test Coverage Report for Build 176

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 88.35%

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Totals
Change from base Build 175:	0.0%
Covered Lines:	140
Relevant Lines:	152

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💛 - Coveralls

[github-actions[bot]]

:tada: This PR is included in version 7.1.1 :tada:

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

Your semantic-release bot :package::rocket: