C#: Fix internal source generator on the 7.0.200 SDK

modules/mono/glue/GodotSharp/Godot.SourceGenerators.Internal/UnmanagedCallbacksGenerator.cs

@@ -168,7 +168,9 @@ using Godot.NativeInterop;
             {
                 var parameter = callback.Parameters[i];
 
-                source.Append(parameter.ToDisplayString());
+                AppendRefKind(source, parameter.RefKind);
+                source.Append(' ');
+                source.Append(parameter.Type.FullQualifiedNameIncludeGlobal());
                 source.Append(' ');
                 source.Append(parameter.Name);