fix bug removing cost schedule columns

it was using _execute though it's not an ifc operator

src/blenderbim/blenderbim/bim/module/cost/operator.py

@@ -544,7 +544,7 @@ class RemoveCostColumn(bpy.types.Operator):
     bl_options = {"REGISTER", "UNDO"}
     name: bpy.props.StringProperty()
 
-    def _execute(self, context):
+    def execute(self, context):
         core.remove_cost_column(tool.Cost, self.name)
         return {"FINISHED"}