misc: always prefer data source over manually defined items (#43689)

wcs/fields.py

@@ -1461,9 +1461,7 @@ class ItemField(WidgetField):
             self.widget_class = JsonpSingleSelectWidget
             return
 
-        if self.items:
-            kwargs['options'] = self.get_options()
-        elif self.data_source:
+        if self.data_source:
             items = data_sources.get_items(self.data_source,
                     include_disabled=self.display_disabled_items)
             kwargs['options'] = [x[:3] for x in items if not x[-1].get('disabled')]