Fixed a couple docstring comments which were out of date after an argument got renamed

Author: tleonhardt

cmd2/cmd2.py

@@ -1973,7 +1973,7 @@ def _restore_output(self, statement: Statement) -> None:
     def _cmd_func(self, command: str) -> Optional[Callable]:
         """
         Get the function for a command
-        :param arg: the name of the command
+        :param command: the name of the command
         """
         func_name = self._cmd_func_name(command)
         if func_name:
@@ -1983,7 +1983,7 @@ def _cmd_func(self, command: str) -> Optional[Callable]:
     def _cmd_func_name(self, command: str) -> str:
         """Get the method name associated with a given command.
 
-        :param arg: command to look up method name which implements it
+        :param command: command to look up method name which implements it
         :return: method name which implements the given command
         """
         target = COMMAND_PREFIX + command