tutorials/06_python_support: Fix tutorial snippet

Signed-off-by: Martin Pecka <[email protected]>

tutorials/06_python_support.md

@@ -340,7 +340,7 @@ We can declare the topic remapping option using the following code:
 
  # Create a transport node and remap a topic.
  nodeOpts = NodeOptions()
- nodeOpts.add_topic_remap("/foo", "/bar")
+ nodeOpts.add_topic_remap("/example_stringmsg_topic", "/bar")
  node = Node(nodeOpts)
 ```