SSH: Switch from public key authentication to password authentication
Solution 1:
The PasswordAuthentication option in the /etc/ssh/sshd_config file controls whether passwords are allowed.
Really, though. Use public keys.
Solution 2:
If you want to do this temporarily, you could connect to the server with ssh -o 'PubkeyAuthentication no' server. If you want to do this permanently, on the server you could remove your public key from ~/.ssh/authorized_keys or on your computer you could add the following to ~/.ssh/config
Hostname server
PubkeyAuthentication no