Version ranges lead to exception

Hi there,

when a package version is defined as e.g. `[2.0.0]` this leads to an exception. This is already commented in the `LockFileHelper`:

```cs
/// See: https://github.com/NuGet/NuGet.Client/blob/538727480d93b7d8474329f90ccb9ff3b3543714/nuget-inspector/NuGet.Core/NuGet.LibraryModel/LibraryRange.cs#L68
/// FIXME: there are some rare cases where we have multiple constraints as in this JSON snippet for FSharp.Core:
/// "projectFileDependencyGroups": {
/// ".NETFramework,Version=v4.7.2": ["FSharp.Core >= 4.3.4 < 5.0.0",]
/// },
/// This a case that is NOT handled yet
```

I just opened this issue to track it. I'll open a PR right away.

Best regards,
G