add uri=

Signed-off-by: Lehui Liu <lehui@anyscale.com>

Author: liulehui

doc/source/train/user-guides/experiment-tracking.rst

@@ -183,7 +183,7 @@ If applicable, make sure that you properly set up credentials on each training w
         .. testcode::
             :skipif: True
 
-            mlflow.set_tracking_uri("file://some_shared_storage_path/mlruns")
+            mlflow.set_tracking_uri(uri="file://some_shared_storage_path/mlruns")
             mlflow.set_experiment("my_experiment")
             mlflow.start_run()