If you do not want to be in a hub you simply leave. Click "Edit Account" from the site header. Click Preferences. You'll see a list of your hub memberships, click "Leave" on any hubs you wish to not be a part of.
If you created a hub admin and wish to leave you may need to promote another admin first. Click "Manage Hub." You'll see a list of hub members, once you've promoted another Admin you can click "Remove" by your own name. You may also remove yourself if you are the only hub member. Done.