Allow ndarray versions < 0.18

[maffoo]

Previously the version constraint was updated to ndarray <= 0.17 but the 0.17 release was yanked and this excludes 0.17.1 and later point releases. This updates the dependency specification to < 0.18 which will allow point releass (and which is closer to what was used before #516).

[Icxolu]

Thank you, but I actually think this is not needed. With these dependencies I can successfully build an extension module.

pyo3 = "0.27"
numpy = "0.27"
ndarray = "0.17.1"

$ cargo tree -i ndarray
ndarray v0.17.1
├── numpy v0.27.1
│   └── pyo3-scratch v0.1.0 (G:\RustProjects\pyo3-workspace\pyo3-scratch)
└── pyo3-scratch v0.1.0 (G:\RustProjects\pyo3-workspace\pyo3-scratch)

So I think <=0.17 and <0.18 are semver equivalent.

[maffoo]

Ah, you are right. I had been trying to run cargo clippy after updating numpy and ndarray, and got errors from two versions of ndarray being included in the build. But running cargo build updated the lockfile and resolved a single version of ndarray, which fixed things.