Bump tokio-stream from 0.1.7 to 0.1.8

Bumps [tokio-stream](https://github.com/tokio-rs/tokio) from 0.1.7 to 0.1.8.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-stream-0.1.7...tokio-stream-0.1.8)

---
updated-dependencies:
- dependency-name: tokio-stream
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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