It's not terribly bothersome because I managed to set it to auto-boot 8.1 after 3 seconds and I normally don't watch my PC boot up but still figured I would ask.
How can I get rid of this?
You can use EasyBCD editor. It is free for personal use.
Go to Edit Boot Menu and delete the entry you don't want. You can also make a backup copy before you do that. If you're afraid to delete an entry then make the timeout 0 seconds.