Layers: Fix exception message

Updates the exception message to report the correct dependency instead
of the layer name itself. Instead of reporting the actual dependency, it
was reporting, for example 'Layer layer_name is depended upon by
layer_name'.

Author: dgmcdona

volatility3/framework/interfaces/layers.py

@@ -678,7 +678,7 @@ def del_layer(self, name: str) -> None:
             if name in self._layers[layer].dependencies:
                 raise exceptions.LayerException(
                     self._layers[layer].name,
-                    f"Layer {self._layers[layer].name} is depended upon by {layer}",
+                    f"Layer {name} is depended upon by {layer}",
                 )
         # Otherwise, wipe out the layer
         self._layers[name].destroy()