How to remove an existing OwnerTeam from the Ownerteam drop down list on incident record in ITSM 7.x?
1. Create a new defintion set in Service Management Administrator logging in as Administrator.
2. Go to StandardUserTeam object and add a new logic field called Terminated.
3. Add this to the StandardUserteam panel.
4. Commit a definition set.
5. Go to Incident object and go to the OwnerTeam field. Edit the OwnerTeam field properties. On the Validation tab, click the advance button add Terminated = False as seen in the screenshot below. This will restrict the list of teams to only ones that are terminated flag is unchecked.