Just fyi in case somebody else gets stuck. I ended up having to edit 2 files.
#1 is /etc/apt/sources.list.d . On there I had the enterprise.proxmox.com line with pve-enterprise at the end. I commented that out.
#deb https://enterprise.proxmox.com/debian/pve bullseye pve-enterprise
#2 was editing the /etc/apt/sources.list file. On there I added the line with the download.proxmox.com (pve-no-subscription) as the Package_Repositories page suggests.
deb http://ftp.us.debian.org/debian bullseye main contrib deb http://ftp.us.debian.org/debian bullseye-updates main contrib # security updates deb http://security.debian.org bullseye-security main contrib deb http://download.proxmox.com/debian/pve bullseye pve-no-subscription
after that I was able to do an apt-get update and apt-get upgrade just fine
