Fix doc for position of captured mouse

The position is not at the center of the screen but of the window.

doc/classes/DisplayServer.xml

@@ -1512,7 +1512,7 @@
 			Makes the mouse cursor hidden if it is visible.
 		</constant>
 		<constant name="MOUSE_MODE_CAPTURED" value="2" enum="MouseMode">
-			Captures the mouse. The mouse will be hidden and its position locked at the center of the screen.
+			Captures the mouse. The mouse will be hidden and its position locked at the center of the window manager's window.
 			[b]Note:[/b] If you want to process the mouse's movement in this mode, you need to use [member InputEventMouseMotion.relative].
 		</constant>
 		<constant name="MOUSE_MODE_CONFINED" value="3" enum="MouseMode">

doc/classes/Input.xml

@@ -397,7 +397,7 @@
 			Makes the mouse cursor hidden if it is visible.
 		</constant>
 		<constant name="MOUSE_MODE_CAPTURED" value="2" enum="MouseMode">
-			Captures the mouse. The mouse will be hidden and its position locked at the center of the screen.
+			Captures the mouse. The mouse will be hidden and its position locked at the center of the window manager's window.
 			[b]Note:[/b] If you want to process the mouse's movement in this mode, you need to use [member InputEventMouseMotion.relative].
 		</constant>
 		<constant name="MOUSE_MODE_CONFINED" value="3" enum="MouseMode">