Update BehaviourTree.md

BehaviourTree.md

@@ -6,7 +6,7 @@
 2. Override `Start` method (optional) and initiate blackboard values, make sure to call `base.Start();` at the start of the method
 3. Override `SetRoot` method, here you can build up your behaviour tree using the `BehaviourTreeBuilder` class as shown below
 4. Attach the script to the GameObject
-5. The nodes `Execute` method will be called every frame
+5. The tree will be executed every frame
 
 ### Example