need to fix xworld3d_navigation example due to api changes

[le-horizon]

--- a/tutorial/examples/xworld3d_navigation.py
+++ b/tutorial/examples/xworld3d_navigation.py
@@ -198,12 +198,13 @@ if __name__ == "__main__":
     # and other settings used by ComputationTask.
     ct_settings = {
         "RL": dict(
-            alg=alg,
+            algorithm=alg,
             show_para_every_backwards=500,
             # sampling
             agent_helper=OnlineHelper,
             # each agent will call `learn()` every `sample_interval` steps
-            sample_interval=4)
+            sample_interval=4,
+            num_agents=num_agents)
     }

@skylian or @yu239-zz, could you help patch the fix?

Thanks