[docs] change MLFlow to MLflow in docs (#13739)

doc/source/tune/api_docs/logging.rst

@@ -162,7 +162,7 @@ CSVLogger
 MLFlowLogger
 ------------
 
-Tune also provides a default logger for `MLFlow <https://mlflow.org>`_. You can install MLFlow via ``pip install mlflow``.
+Tune also provides a default logger for `MLflow <https://mlflow.org>`_. You can install MLflow via ``pip install mlflow``.
 You can see the :doc:`tutorial here </tune/tutorials/tune-mlflow>`.
 
 WandbLogger