NuGetUtils.IsNuSpec can miss nuspec files

This conditional seems a bit off?

https://github.com/dotnet/arcade/blob/b417c781006458ea6d1ca37fd9c4376580b7c521/src/Microsoft.DotNet.NuGetRepack/tasks/src/NuGetUtils.cs#L23

For example, after building the VMR, `dotnet/src/fsharp/artifacts/packages/Release/Dependency/Shipping/FSharp.Compiler.Service.43.10.100-dev.nupkg` has the following `ZipArchiveEntry.FullName`s:

```
_rels/.rels
FSharp.Compiler.Service.nuspec
Icon.png
lib/netstandard2.0/FSharp.Compiler.Service.dll
lib/netstandard2.0/FSharp.Compiler.Service.xml
lib/netstandard2.0/FSharp.DependencyManager.Nuget.dll
lib/netstandard2.0/FSharp.DependencyManager.Nuget.xml
lib/netstandard2.0/default.win32manifest
lib/netstandard2.0/de/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/es/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/cs/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/ko/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/it/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/ja/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/fr/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/ru/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/pt-BR/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/zh-Hans/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/tr/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/zh-Hant/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/pl/FSharp.Compiler.Service.resources.dll
lib/netstandard2.0/de/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/cs/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/es/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/ko/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/ja/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/pl/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/it/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/fr/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/pt-BR/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/ru/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/zh-Hans/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/tr/FSharp.DependencyManager.Nuget.resources.dll
lib/netstandard2.0/zh-Hant/FSharp.DependencyManager.Nuget.resources.dll
[Content_Types].xml
package/services/metadata/core-properties/8488899054c34cc3ae0c8d31aaaf8ce8.psmdcp
```

And so `NuGetUtils.IsNuspecFile` returns false for the nuspec file. Is this intentional?