Editor Tests targeting static abstract members should use at least Net 6 reference assemblies

[AlekseyTs]

Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterfaceOperator_ImplementExplicitly [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterface_ImplementExplicitly [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterface_Implicitly [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterfaceMemberExplicitly [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterface_ImplementAbstractly [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterfaceOperator_ImplementImplicitly [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterfaceOperator_OnlyExplicitlyImplementable [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterfaceMember_ImplementAbstractly [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterface_ImplementImplicitly [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterfaceMember [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterfaceOperator_ImplementAbstractly [FAIL]
Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.ImplementInterface.ImplementInterfaceTests.TestStaticAbstractInterface_Explicitly [FAIL]

[AlekseyTs]

The tests are going to be disabled for now.

[jinujoseph]

cc @JoeRobich