Update nntplib to Python 3.11

Lib/nntplib.py

@@ -68,6 +68,7 @@ import socket
 import collections
 import datetime
 import sys
+import warnings
 
 try:
     import ssl
@@ -85,6 +86,8 @@ __all__ = ["NNTP",
            "decode_header",
            ]
 
+warnings._deprecated(__name__, remove=(3, 13))
+
 # maximal line length when calling readline(). This is to prevent
 # reading arbitrary length lines. RFC 3977 limits NNTP line length to
 # 512 characters, including CRLF. We have selected 2048 just to be on