Fix missing MLClient parameter (workspace_name)

I added the `workspace_name=workspace_name` to the MLClient constructor. 
Without this parameter, the next example statement on line 72 `mlflow_tracking_uri = ml_client.workspaces.get(ml_client.workspace_name).mlflow_tracking_uri` fails with the error "ValidationException: Please provide a workspace name or use a MLClient with a workspace name set."

By providing the workspace_name to the MLClient constructor the error is prevented.

Author: timschonborn

includes/machine-learning-mlflow-configure-tracking.md

@@ -59,7 +59,8 @@ ms.author: fasantia
     
         ml_client = MLClient(credential=DefaultAzureCredential(),
                                 subscription_id=subscription_id, 
-                                resource_group_name=resource_group)
+                                resource_group_name=resource_group,
+                                workspace_name=workspace_name)
         ```
 
         > [!IMPORTANT]
@@ -123,4 +124,4 @@ ms.author: fasantia
     ---
 
     > [!TIP]
-    > When working on shared environments, like an Azure Databricks cluster, Azure Synapse Analytics cluster, or similar, it is useful to set the environment variable `MLFLOW_TRACKING_URI` at the cluster level to automatically configure the MLflow tracking URI to point to Azure Machine Learning for all the sessions running in the cluster rather than to do it on a per-session basis.
+    > When working on shared environments, like an Azure Databricks cluster, Azure Synapse Analytics cluster, or similar, it is useful to set the environment variable `MLFLOW_TRACKING_URI` at the cluster level to automatically configure the MLflow tracking URI to point to Azure Machine Learning for all the sessions running in the cluster rather than to do it on a per-session basis.