See discussion at https://redhat-internal.slack.com/archives/C04KQHS01B5/p1726497455640869
There are no longer any SKUs that use syspurpose addons. Additionally, the addons command is being removed from subscription-manager in RHEL10. So we are free to remove addons from the Katello UI:
Activation key details
New activation key details
System Purpose card (host details)
QE Tracker for https://issues.redhat.com/browse/SAT-28026