`dotnet-getdocument` fails to resolve GetDocument.Insider for net7.0

[captainsafia]

While validating https://github.com/dotnet/aspnetcore/issues/43395, I realized that https://github.com/dotnet/aspnetcore/pull/43701 broke resolution for the GetDocument.Insider assembly in the dotnet-getdocument tool.

Build FAILED.

/Users/captainsafia/.nuget/packages/microsoft.extensions.apidescription.server/7.0.0-rtm.22471.6/build/Microsoft.Extensions.ApiDescription.Server.targets(66,5): error : The application to execute does not exist: '/Users/captainsafia/.nuget/packages/microsoft.extensions.apidescription.server/7.0.0-rtm.22471.6/tools/net7.0/GetDocument.Insider.dll' [/Users/captainsafia/tests/OpenApiThreading/OpenApiThreading.csproj]
/Users/captainsafia/.nuget/packages/microsoft.extensions.apidescription.server/7.0.0-rtm.22471.6/build/Microsoft.Extensions.ApiDescription.Server.targets(66,5): error MSB3073: The command "dotnet "/Users/captainsafia/.nuget/packages/microsoft.extensions.apidescription.server/7.0.0-rtm.22471.6/build/../tools/dotnet-getdocument.dll" --assembly "/Users/captainsafia/tests/OpenApiThreading/bin/Debug/net7.0/OpenApiThreading.dll" --file-list "obj/OpenApiThreading.OpenApiFiles.cache" --framework ".NETCoreApp,Version=v7.0" --output "obj/" --project "OpenApiThreading" --assets-file "/Users/captainsafia/tests/OpenApiThreading/obj/project.assets.json" --platform "AnyCPU" " exited with code 129. [/Users/captainsafia/tests/OpenApiThreading/OpenApiThreading.csproj]

It looks like the NuSpec needs to be updated to package the net7.0 assembly correctly.