Update hello_collision.adoc

Corrected debug of bulletAppState to reflect 3.1 stable.

src/docs/asciidoc/jme3/beginner/hello_collision.adoc

@@ -87,7 +87,7 @@ public class HelloCollision extends SimpleApplication
     /** Set up Physics */
     bulletAppState = new BulletAppState();
     stateManager.attach(bulletAppState);
-    //bulletAppState.getPhysicsSpace().enableDebug(assetManager);
+    //bulletAppState.setDebugEnabled(true);
 
     // We re-use the flyby camera for rotation, while positioning is handled by physics
     viewPort.setBackgroundColor(new ColorRGBA(0.7f, 0.8f, 1f, 1f));
@@ -345,7 +345,7 @@ Again, you create a CollisionShape: This time you choose a CapsuleCollisionShape
 
 [source,java]
 ----
-bulletAppState.getPhysicsSpace().enableDebug(assetManager);
+bulletAppState.setDebugEnabled(true);
 ----