Bump tokio-test from 0.4.1 to 0.4.2 in /cmd/pinniped-proxy (#2817)

Bumps [tokio-test](https://github.com/tokio-rs/tokio) from 0.4.1 to 0.4.2.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-test-0.4.1...tokio-test-0.4.2)

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