updated description of Array.shuffle to properly describe that it uses the same common seed at every runtime, thus being reproducible in general

doc/classes/Array.xml

@@ -291,7 +291,7 @@
 		</method>
 		<method name="shuffle">
 			<description>
-				Shuffles the array such that the items will have a random order.
+				Shuffles the array such that the items will have a random order. This method uses the global random number generator common to methods such as [method @GDScript.randi]. Call [method @GDScript.randomize] to ensure that a new seed will be used each time if you want non-reproducible shuffling.
 			</description>
 		</method>
 		<method name="size">