In order to remove a prompt that you have set using the CatOS, you must clear the configuration. You can just clear the system specific configuration (clear config system) and remove the prompt setting (keep reading!).
This will unfortunately clear anything that is a non-default setting under this section of the configuration. You can view that portion of the config with the command (show config system).
This is not a bug, it is simply the way it works. In the original CatOS code, the prompt did not follow the system name, you had to set both parameters on the switch. As the code evolved, Cisco changed the OS so that, if the prompt is the default, the OS would insert the system name into the prompt. However once the prompt was set, the only way to get it to follow the system name again is to clear the configuration.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...