Modify team unregistration to cancel registration instead of deleting

tournaments/services/tournament_unregistration.py

@@ -110,9 +110,9 @@ class TournamentUnregistrationService:
 
     def _delete_registered_team(self):
         team_registration = self.player_registration.team_registration
-        team_registration.delete()
-        # team_registration.cancel_registration()
-        # team_registration.save()
+        # team_registration.delete()
+        team_registration.cancel_registration()
+        team_registration.save()
 
     def _cleanup_session(self):
         self.request.session['team_registration'] = []