add callback step to doc

Author: jerrypeng7773

doc/workflows/pipelines/sagemaker.workflow.pipelines.rst

@@ -109,15 +109,17 @@ Steps
 
 .. autoclass:: sagemaker.workflow.steps.TrainingStep
 
-.. autoclass:: sagemaker.workflow.steps.CreateModelStep
+.. autofunction:: sagemaker.workflow.steps.TuningStep.get_top_model_s3_uri
+
+.. autoclass:: sagemaker.workflow.steps.TuningStep
 
 .. autoclass:: sagemaker.workflow.steps.TransformStep
 
 .. autoclass:: sagemaker.workflow.steps.ProcessingStep
 
-.. autoclass:: sagemaker.workflow.steps.TuningStep
+.. autoclass:: sagemaker.workflow.steps.CreateModelStep
 
-.. autofunction:: sagemaker.workflow.steps.TuningStep.get_top_model_s3_uri
+.. autoclass:: sagemaker.workflow.callback_step.CallbackStep
 
 Utilities
 ---------