Fix area_shape_exited's description

area_shape_entered and area_shape_exited had the exact same description. Changed area_shape_exited's description to specify that the signal is emitted when another area's shape exits rather than enters this area's shapes.

doc/classes/Area3D.xml

@@ -138,7 +138,7 @@
 			<argument index="2" name="area_shape_index" type="int" />
 			<argument index="3" name="local_shape_index" type="int" />
 			<description>
-				Emitted when one of another Area3D's [Shape3D]s enters one of this Area3D's [Shape3D]s. Requires [member monitoring] to be set to [code]true[/code].
+				Emitted when one of another Area3D's [Shape3D]s exits one of this Area3D's [Shape3D]s. Requires [member monitoring] to be set to [code]true[/code].
 				[code]area_rid[/code] the [RID] of the other Area3D's [CollisionObject3D] used by the [PhysicsServer3D].
 				[code]area[/code] the other Area3D.
 				[code]area_shape_index[/code] the index of the [Shape3D] of the other Area3D used by the [PhysicsServer3D]. Get the [CollisionShape3D] node with [code]area.shape_owner_get_owner(area_shape_index)[/code].