Derive default on ReportExecutionOrderAmbiguities (#4873)

crates/bevy_ecs/src/schedule/stage.rs

@@ -47,6 +47,7 @@ impl_downcast!(Stage);
 ///
 /// The checker may report a system more times than the amount of constraints it would actually need
 /// to have unambiguous order with regards to a group of already-constrained systems.
+#[derive(Default)]
 pub struct ReportExecutionOrderAmbiguities;
 
 /// Stores and executes systems. Execution order is not defined unless explicitly specified;

examples/ecs/ecs_guide.rs

@@ -334,7 +334,7 @@ fn main() {
         // Be aware that not everything reported by this checker is a potential problem, you'll have
         // to make that judgement yourself.
         .add_plugin(LogPlugin::default())
-        .insert_resource(ReportExecutionOrderAmbiguities)
+        .init_resource::<ReportExecutionOrderAmbiguities>()
         // This call to run() starts the app we just built!
         .run();
 }