Remove validation suppression from System.Runtime.Serialization.Primitives

[chcosta]

We're suppressing validation in System.Runtime.Serialization.Primitives until we can oob it to desktop.

[SGuyGe]

@chcosta What's this about? Is there a main issue that we can reference to?

[chcosta]

This is a packaging issue. This issue is just tracking that there is cleanup work for us to be done for this library when we can OOB this package to desktop. https://github.com/dotnet/corefx/blob/master/src/System.Runtime.Serialization.Primitives/pkg/ValidationSuppression.txt#L2

[chcosta]

@ericstj , can we remove this now?

[ericstj]

Yep, so long as you don't get any validation errors. It looks like the need for this was fixed with dotnet/corefx@5fed590.