fixed unused var warning

Author: Matthias Radestock

src/gen_server2.erl

@@ -440,7 +440,7 @@ unregister_name(Pid) when is_pid(Pid) ->
     Pid;
 % Under R12 let's just ignore it, as we have a single term as Name.
 % On R13 it will never get here, as we get tuple with 'local/global' atom.
-unregister_name(Name) -> ok.
+unregister_name(_Name) -> ok.
 
 extend_backoff(undefined) ->
     undefined;