GetDependencies API endpoint docs includes NUGET

I noticed the docs for the API mention that GetDependencies `versionKey.system` can be one of `GO`, `NPM`, `CARGO`, `MAVEN`, `PYPI`, `NUGET`

https://docs.deps.dev/api/v3alpha/#getdependencies

However, the docs mention that this endpoint is not available for nuget

```
GetDependencies returns a resolved dependency graph for the given package version. Dependencies are currently available for Go, npm, Cargo, Maven and PyPI.
```

The API gives a 404 for any nuget, so it's just the docs that need to be updated

404 -> https://api.deps.dev/v3alpha/systems/nuget/packages/azure.core/versions/1.25.0:dependencies