Update ndarray requirement from ^0.15.6 to ^0.16.1

Updates the requirements on [ndarray](https://github.com/rust-ndarray/ndarray) to permit the latest version.
- [Release notes](https://github.com/rust-ndarray/ndarray/releases)
- [Changelog](https://github.com/rust-ndarray/ndarray/blob/master/RELEASES.md)
- [Commits](rust-ndarray/ndarray@0.15.6...0.16.1)

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

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

Author: dependabot[bot]

Cargo.toml

@@ -14,7 +14,7 @@ crate-type = ["cdylib"]
 
 [dependencies]
 approx = "^0.5.1"
-ndarray = "^0.15.6"
+ndarray = "^0.16.1"
 num-traits = "^0.2.19"
 pyo3 = { version = "^0.21.1", features = ["extension-module", "abi3-py38"], optional = true }
 numpy = { version = "^0.21.0", optional = true }