[coreml] Update to beta 6 (#2531)

Fix our rdar 33643011 where additional setters were added in the headers
but did not exists.

src/coreml.cs

@@ -78,19 +78,14 @@ namespace XamCore.CoreML {
 
 		// Category MLFeatureDescription (MLFeatureValueConstraints)
 
-		// HACK: radar://33643011 -> https://trello.com/c/ZN712GOi
-
-		// [FAIL] Selector not found for CoreML.MLFeatureDescription : setMultiArrayConstraint:
 		[NullAllowed, Export ("multiArrayConstraint", ArgumentSemantic.Assign)]
-		MLMultiArrayConstraint MultiArrayConstraint { get; /*set;*/ }
+		MLMultiArrayConstraint MultiArrayConstraint { get; }
 
-		// [FAIL] Selector not found for CoreML.MLFeatureDescription : setImageConstraint:
 		[NullAllowed, Export ("imageConstraint", ArgumentSemantic.Assign)]
-		MLImageConstraint ImageConstraint { get; /*set;*/ }
+		MLImageConstraint ImageConstraint { get; }
 
-		// [FAIL] Selector not found for CoreML.MLFeatureDescription : setDictionaryConstraint:
 		[NullAllowed, Export ("dictionaryConstraint", ArgumentSemantic.Assign)]
-		MLDictionaryConstraint DictionaryConstraint { get; /*set;*/ }
+		MLDictionaryConstraint DictionaryConstraint { get; }
 	}
 
 	interface IMLFeatureProvider { }