Remove RunApiCompat switch from APICompat and PackageValidation

[ViktorHofer]

sdk/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.ApiCompat.ValidatePackage.targets

Line 47 in 4f3276d

RunApiCompat="$(RunApiCompat)"

That switch should never have been added to the new APICompat. It causes APICompat to not run when using PackageValidation. That means package validation checks PKVxxxx are performed but APICompat work items aren't enqueued.

I can't think of any scenario where we would want that except for APICompat's own integration tests (which is the reason why the property was added).

@dotnet/area-infrastructure-libraries a new issue has been filed in the ApiCompat area, please triage