Bluehost has two ways to delete email forwarders, and currently only one way works.

The method that doesn't work

Go to Hosting > Email > Forwarding, and you'll arrive at a URL like https://my.bluehost.com/cgi/email_manager/forwarders/delete/. This is what the page looks like:

From here you can click on delete next to the forwarder, and it'll ask Are you sure? Click Are you sure, and the page reloads. Then at the top a message says Email forwarder removed. But the forwarder is still there!

The method that works

Go to Hosting > Cpanel > Forwarders, and you'll reach a URL like https://login.bluehost.com/frontend/bluehost/mail/fwds.html. This is what you should see:

From here you can delete email forwarders. Yay!