add nested kedy agin in mlflow.yml

kedro_mlflow/template/project/mlflow.yml

@@ -40,6 +40,7 @@ tracking:
   run:
     id: null # if `id` is None, a new run will be created
     name: null # if `name` is None, pipeline name will be used for the run name. You can use "${km.random_name:}" to generate a random name (mlflow's default)
+    nested: True  # if `nested` is False, you won't be able to launch sub-runs inside your nodes
   params:
     dict_params:
       flatten: False  # if True, parameter which are dictionary will be splitted in multiple parameters when logged in mlflow, one for each key.