build(deps): update ndarray requirement from 0.14 to 0.15

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](https://github.com/rust-ndarray/ndarray/compare/ndarray-rand-0.14.0...0.15.1)

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

Cargo.toml

@@ -19,7 +19,7 @@ nalgebra-bindings = ["nalgebra"]
 datasets = []
 
 [dependencies]
-ndarray = { version = "0.14", optional = true }
+ndarray = { version = "0.15", optional = true }
 nalgebra = { version = "0.23.0", optional = true }
 num-traits = "0.2.12"
 num = "0.3.0"