How to reset/remove authentication supplied for remote file access in Explorer?
If you didn't click "Remember password": Reboot, or log out from Windows. (Also, next time use net use to establish the connection – it doesn't cache passwords at all, so it's enough to disconnect via net use /d, whereas Windows Explorer caches passwords until logout.
If you did click "Remember password": Open the Credential Manager control panel, go to the "Windows Credentials" section and delete things from there. (You can also do this using cmdkey.) Then reboot the system, or log out from Windows.