Fix copy-paste error in CacheProxyConnection server version check

The condition on line 1417 incorrectly checked 'server_ver is None or server_ver is None'
when it should check 'server_ver is None or server_name is None'.

This bug would allow server_name to be None without raising an error, which would
then cause issues when server_name is used later in the comparison at line 1424.

Author: Nepomuk5665

redis/connection.py

@@ -1414,7 +1414,7 @@ def connect(self):
         server_ver = self._conn.handshake_metadata.get(b"version", None)
         if server_ver is None:
             server_ver = self._conn.handshake_metadata.get("version", None)
-        if server_ver is None or server_ver is None:
+        if server_ver is None or server_name is None:
             raise ConnectionError("Cannot retrieve information about server version")
 
         server_ver = ensure_string(server_ver)