Added missing param docs.

src/Avalonia.Controls/Primitives/TemplatedControl.cs

@@ -387,6 +387,7 @@ namespace Avalonia.Controls.Primitives
         /// Sets the TemplatedParent property for the created template children.
         /// </summary>
         /// <param name="control">The control.</param>
+        /// <param name="templatedParent">The templated parent to apply.</param>
         internal static void ApplyTemplatedParent(IStyledElement control, ITemplatedControl? templatedParent)
         {
             control.SetValue(TemplatedParentProperty, templatedParent);