Note: This isn't a duplicate of How to remove Unity web apps?
I created some web apps with Firefox before installing Chromium. Now that I'm using Chromium as my default browser, when I click on these web apps shortcuts, it opens in Chromium in a special window that can't create new tabs, but it doesn't integrate with the menu bar indicators like it should. However, Chromium doesn't ask if I'd like to create a shortcut. How can I remove the shortcuts that I created in Firefox so that I can re-create them with Chromium?
I followed the instructions in the link to the question I posted above and uninstalled the unity-webapps-* packages for the few webapps I enabled using Firefox, but the shortcuts are still there and Chromium still doesn't want to create new ones.
How can I fix this?