Iriun Web Camera on the Mac is a bit of a pain to uninstall. Utilities like AppCleaner will not completely uninstall all the Iriun as it doesn't know about the services that run in the background, which will continue to run the background of your computer regardless if it's uninstalled or not.
Fire up Activity monitor, and search for iriun, and force quit any tasks it has operating (there should be at least two).
Next, you'll need to delete the following (this will be from the library located at the root of your boot volume, not in your /Users/ ):
These will likely require your admin password to delete. That's it. Enjoy your Iriun free life as it'll stop popping up as an input option.