Part: modernize C++: use range-based for loop

src/Mod/Part/App/ExtrusionHelper.cpp

@@ -284,8 +284,8 @@ void ExtrusionHelper::makeDraft(const TopoDS_Shape& shape,
             }
             else
                 // we already have the results
-                for (auto it = shells.begin(); it != shells.end(); ++it)
-                    drafts.push_back(*it);
+                for (const auto & shell : shells)
+                    drafts.push_back(shell);
         }
         else { // no solid
             BRepBuilderAPI_Sewing sewer;