Fix docs about asyncio.start_server()

Author: beavailable

Doc/library/asyncio-stream.rst

@@ -92,7 +92,8 @@ and work with streams:
                           family=socket.AF_UNSPEC, \
                           flags=socket.AI_PASSIVE, sock=None, \
                           backlog=100, ssl=None, reuse_address=None, \
-                          reuse_port=None, ssl_handshake_timeout=None, \
+                          reuse_port=None, keep_alive=None, \
+                          ssl_handshake_timeout=None, \
                           ssl_shutdown_timeout=None, start_serving=True)
 
    Start a socket server.