Fix typing issue

plugins/CuraEngineBackend/CuraEngineBackend.py

@@ -542,7 +542,7 @@ class CuraEngineBackend(QObject, Backend):
     ##  Remove old layer data (if any)
     def _clearLayerData(self, build_plate_numbers: Set = None) -> None:
         # Clear out any old gcode
-        self._scene.gcode_dict = {}  # type: dict
+        self._scene.gcode_dict = {}  # type: ignore
 
         for node in DepthFirstIterator(self._scene.getRoot()): #type: ignore #Ignore type error because iter() should get called automatically by Python syntax.
             if node.callDecoration("getLayerData"):