remove global decl about unused variable

Lib/ftplib.py

@@ -245,7 +245,6 @@ class FTP:
 
     def makeport(self):
         '''Create a new socket and send a PORT command for it.'''
-        global nextport
         sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
         sock.bind(('', 0))
         sock.listen(1)