build(deps): bump pyo3 in /examples/namespace_package

Bumps [pyo3](https://github.com/pyo3/pyo3) from 0.16.2 to 0.16.4.
- [Release notes](https://github.com/pyo3/pyo3/releases)
- [Changelog](https://github.com/PyO3/pyo3/blob/main/CHANGELOG.md)
- [Commits](PyO3/pyo3@v0.16.2...v0.16.4)

---
updated-dependencies:
- dependency-name: pyo3
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

examples/namespace_package/Cargo.lock

@@ -7,4 +7,4 @@ edition = "2018"
 crate-type = ["cdylib"]
 
 [dependencies]
-pyo3 = { version = "0.16.2", features = ["extension-module"] }
+pyo3 = { version = "0.16.4", features = ["extension-module"] }