removes network os guess static method (#19467)

For devices that do not support mutliplexing, we cannot automatically
determine the network os.  This removes the os guess static method
from the terminal plugin.  For this devices, the network_os
value must be configured

lib/ansible/plugins/terminal/ios.py

@@ -80,9 +80,3 @@ class TerminalModule(TerminalBase):
             self._exec_cli_command('disable')
 
 
-    @staticmethod
-    def guess_network_os(conn):
-        stdin, stdout, stderr = conn.exec_command('show version')
-        if 'Cisco IOS Software' in stdout.read():
-            return 'ios'
-