Docs fix: add execution config to MWAA code example (#667) (#674)

Add execution config to MWAA code example document.

Closes: #667
(cherry picked from commit 773fa27)

docs/getting_started/mwaa.rst

@@ -87,8 +87,9 @@ In your ``my_cosmos_dag.py`` file, import the ``DbtDag`` class from Cosmos and c
 
 .. code-block:: python
 
-    from cosmos import DbtDag, ProjectConfig, ProfileConfig
+    from cosmos import DbtDag, ProjectConfig, ProfileConfig, ExecutionConfig
     from cosmos.profiles import PostgresUserPasswordProfileMapping
+    from cosmos.constants import ExecutionMode
 
     profile_config = ProfileConfig(
         profile_name="default",
@@ -99,11 +100,17 @@ In your ``my_cosmos_dag.py`` file, import the ``DbtDag`` class from Cosmos and c
         ),
     )
 
+    execution_config = ExecutionConfig(
+        dbt_executable_path=f"{os.environ['AIRFLOW_HOME']}/dbt_venv/bin/dbt",
+        execution_mode=ExecutionMode.VIRTUALENV,
+    )
+
     my_cosmos_dag = DbtDag(
         project_config=ProjectConfig(
             "<my_dbt_project>",
         ),
         profile_config=profile_config,
+        execution_config=execution_config,
         # normal dag parameters
         schedule_interval="@daily",
         start_date=datetime(2023, 1, 1),