ade: Use decode() function to bytes object

`subprocess.PIPE` returns a bytes object which has no attribute
`read`.

Signed-off-by: Justin Kim <justin.kim@collabora.com>
Reviewed-by: Emanuele Aina <emanuele.aina@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D5358

tools/ade

@@ -291,7 +291,7 @@ class Simulator:
 
     def _exec(self, *args):
         r = subprocess.run(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-        return r.stdout.read().decode().strip()
+        return r.stdout.decode().strip()
 
     def install(self, bundle):
         self._exec('ribchesterctl', 'remove', bundle.id)