How do I turn off minimize-on-click option for Ubuntu dock?

You can revert to the default option by running

gsettings reset org.gnome.shell.extensions.dash-to-dock click-action

Also try running

gsettings range org.gnome.shell.extensions.dash-to-dock click-action

then you'll get all possible values that can be set. See if you find another option preferable.

Use:

gsettings set org.gnome.shell.extensions.dash-to-dock click-action 'minimize-or-overview'

This does exactly what you want it to do.

For those who are looking for a Windows-like "click-action", use:

gsettings set org.gnome.shell.extensions.dash-to-dock click-action 'minimize-or-previews'