How do I edit /etc/runit/1 without logging in?

I made the mistake of autostarting syncthing with runit and now I can't login. (I added "syncthing to /etc/runit/1".) Initially, I rebooted normally to syncthing starting, but from there I could not gain control with ctrl + c. I then tried booting into recovery mode from Grub, but had similar results of ctrl + c not working. Ideally, I would like to delete the syncthing line from the runit file without having to login with another computer or taking out the hard drive. How should I go about fixing this problem.