TCPServer: Fixed typo in class docstring.

Backport candidate.
diff --git a/Lib/SocketServer.py b/Lib/SocketServer.py
index 270f4cd..dee56da 100644
--- a/Lib/SocketServer.py
+++ b/Lib/SocketServer.py
@@ -304,7 +304,7 @@
     - address_family
     - socket_type
     - request_queue_size (only for stream sockets)
-    - reuse_address
+    - allow_reuse_address
 
     Instance variables: