Mention that look_at() expects global coordinates

doc/classes/Node2D.xml

@@ -52,7 +52,7 @@
 			<argument index="0" name="point" type="Vector2">
 			</argument>
 			<description>
-				Rotates the node so it points towards the [code]point[/code].
+				Rotates the node so it points towards the [code]point[/code], which is expected to use global coordinates.
 			</description>
 		</method>
 		<method name="move_local_x">