Fix unary negation on types with builtin operators

- I ran into this on negating a Vector3. Udon is breaking naming convention again with this. Add a special condition for it...

Assets/UdonSharp/Editor/UdonSharpASTVisitor.cs

@@ -928,6 +928,8 @@ private MethodInfo[] GetOperators(System.Type type, BuiltinOperatorType builtinO
             string operatorName = System.Enum.GetName(typeof(BuiltinOperatorType), builtinOperatorType);
             if (builtinOperatorType == BuiltinOperatorType.Multiplication)
                 operatorName = "Multiply"; // Udon breaks standard naming with its multiplication overrides on base types
+            else if (builtinOperatorType == BuiltinOperatorType.UnaryMinus)
+                operatorName = "UnaryNegation";
 
             operatorName = $"op_{operatorName}";