Echo: fix comment, groups is a tuple, not a list

modules/Echo.py

@@ -63,7 +63,7 @@ class Echo(Module):
             userhost    source userhost (unused)
             event       IRC event, used in IRC reply, or none for direct call
             from_admin  whether or not the event came from an admin (unused)
-            groups      list length 1, the message to echo
+            groups      tuple length 1, the message to echo
 
         """