remove redundant time :f32 from harness callbacks. it can be access via run_state.time

examples2d/add_remove2.rs

@@ -10,7 +10,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let rad = 0.5;
 
     // Callback that will be executed on the main loop to handle proximities.
-    testbed.harness_mut().add_callback(move |physics, _, _, _| {
+    testbed.harness_mut().add_callback(move |physics, _, _| {
         let rigid_body = RigidBodyBuilder::new_dynamic()
             .translation(0.0, 10.0)
             .build();