revise heading levels

Author: sdgilley

articles/machine-learning/tutorial-power-bi-custom-model.md

@@ -225,7 +225,7 @@ def run(data):
         return error
 ```
 
-### Define the custom environment
+## Define the custom environment
 
 Next, define the environment to score the model. In the environment, define the Python packages, such as pandas and scikit-learn, that the scoring script (*score.py*) requires.
 
@@ -249,7 +249,7 @@ environment.python.conda_dependencies = CondaDependencies.create(pip_packages=[
 inference_config = InferenceConfig(entry_script='./score.py',environment=environment)
 ```
 
-### Deploy the model
+## Deploy the model
 
 To deploy the model, copy the following code and paste it into a new *code cell* in your notebook: