Demo py-trees-demo-blackboard-namespaces code and image inconsistent

[songyuc]

In the demo py-trees-demo-blackboard-namespaces, I noticed the code and image are inconsistent.

In the demo image, it shows:

Blackboard Client
   Client Data
      name                   : Global
      namespace          : /
      unique_identifier : 7b4b6fb3-d677-4e54-b0e9-3100c58fc236                   
      read                     : set()
      write                    : {'/foo', '/bar', '/parameters/default_speed'}
Variables
   /foo                      : foo 
   /bar                      : bar
   /parameters/default_speed : 20.0

Blackboard Client

Client Data name

: Parameters namespace

:/parameters

unique_identifier:e20f76b8-4767-4552-92b5-2535cd970d66 read

:set() write

:{'/parameters/aggresstve_speed'} Variables

/parameters/aggressive_speed :60.0 

But there seems to be no "speed" variable in the actual code.

Please consider updating the demo. Let me know if any other details are needed!