Update numpy requirement from 0.20 to 0.21

Updates the requirements on [numpy](https://github.com/PyO3/rust-numpy) to permit the latest version.
- [Release notes](https://github.com/PyO3/rust-numpy/releases)
- [Changelog](https://github.com/PyO3/rust-numpy/blob/main/CHANGELOG.md)
- [Commits](PyO3/rust-numpy@v0.20.0...v0.20.0)

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

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

Cargo.toml

@@ -14,7 +14,7 @@ extern = []
 python = ["dep:numpy", "dep:pyo3"]
 
 [dependencies]
-numpy = {version = "0.20", optional = true}
+numpy = {version = "0.21", optional = true}
 pyo3 = {version = "0.20", features = ["extension-module"], optional = true}
 rand = "0.8.5"
 rand_distr = "0.4.3"