Fix: Missing super().__del__() in Cycles and Hydra render engine

According to the Python API release notes, this is required now along
with super().__init__() which was already done.

Also fixes mistake in example in API docs.

Pull Request: https://projects.blender.org/blender/blender/pulls/132476

scripts/modules/bpy_types.py

@@ -1351,6 +1351,7 @@ class HydraRenderEngine(RenderEngine):
             if self.engine_ptr:
                 import _bpy_hydra
                 _bpy_hydra.engine_free(self.engine_ptr)
+        super().__del__()
 
     def get_render_settings(self, engine_type: str):
         """