Add comment in run uc python script why lag exporter need to be deleted.

execution/run_uc.py

@@ -259,6 +259,8 @@ def delete_topics(topics):
     return
 
 
+# Stop the lag exporter in order to reset it and allow smooth execution for
+# next use cases
 def stop_lag_exporter():
     print('Stop the lag exporter')
 
@@ -308,5 +310,6 @@ def main():
     print('---------------------')
     stop_lag_exporter()
 
+
 if __name__ == '__main__':
     main()