build(deps): update pyo3 requirement from 0.18 to 0.19

Updates the requirements on [pyo3](https://github.com/pyo3/pyo3) to permit the latest version.
- [Release notes](https://github.com/pyo3/pyo3/releases)
- [Changelog](https://github.com/PyO3/pyo3/blob/main/CHANGELOG.md)
- [Commits](PyO3/pyo3@v0.18.0...v0.19.0)

---
updated-dependencies:
- dependency-name: pyo3
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.toml

@@ -29,7 +29,7 @@ prost-types = { version = "0.11.0", optional = true }
 async-std = { version = "1", features = ["attributes"] }
 criterion = "0.5"
 http-types = "2"
-pyo3 = "0.18"
+pyo3 = "0.19"
 quickcheck = "1"
 rand = "0.8.4"
 tide = "0.16"