Remove MicrosoftNetFrameworkReferenceAssembliesVersion

[ViktorHofer]

Superseded by the MicrosoftNETFrameworkReferenceAssembliesLatestPackageVersion property which is exposed by the shipping SDK.
The feature in Arcade to reference the netframework reference assemblies was removed in 0f412eb but the MicrosoftNetFrameworkReferenceAssembliesVersion property was missed.

For more details see discussion in dotnet/runtime#60555 (comment).

To double check:

• The right tests are in and and the right validation has happened. Guidance: https://github.com/dotnet/core-eng/tree/master/Documentation/Validation

[ViktorHofer]

cc @dotnet/roslyn-infrastructure FYI as you are still using that property in both roslyn and roslyn-tools. You probably want to remove its usage in favor of the SDK one. Note that this change should be non breaking for you, as you define the property yourself in Versions.props.
cc @MichaelSimons @marcpopMSFT as dotnet/installer uses the property here: https://github.com/dotnet/installer/blob/1a39c5ae6e482cf9249b9042d2aafaa58da00bda/src/SourceBuild/tarball/content/repos/aspnetcore.proj#L14.

[eerhardt]

Thanks!

[eerhardt]

One small request in the above description, just in case someone reads this later:

Superseded by the MicrosoftNetFrameworkReferenceAssembliesVersion property which is exposed by the shipping SDK.

The property name is not correct. It should read:

"Superseded by the MicrosoftNETFrameworkReferenceAssembliesLatestPackageVersion property which is exposed by the shipping SDK."

[ViktorHofer]

Thanks. Copy-paste error. Fixed.