Disabling expired, inactive, or otherwise anomalous accounts supports the concepts of least privilege and least functionality which reduce the attack surface of the system.
Check
Verify the web server is configured to disable accounts when the accounts are no longer associated to a user.
If the web server is not configured to disable accounts when the accounts are no longer associated to a user, this is a finding.
Fix
Configure the web server to disable accounts when the accounts are no longer associated to a user.