Replace single_threaded -> parallel

Author: james7132

crates/bevy_ecs/src/system/system_piping.rs

@@ -202,7 +202,7 @@ pub mod adapter {
     /// // Building a new schedule/app...
     /// # use bevy_ecs::schedule::SystemStage;
     /// # let mut sched = Schedule::default(); sched
-    /// #     .add_stage(CoreStage::Update, SystemStage::single_threaded())
+    /// #     .add_stage(CoreStage::Update, SystemStage::parallel())
     ///     .add_system_to_stage(
     ///         CoreStage::Update,
     ///         // Panic if the load system returns an error.
@@ -246,7 +246,7 @@ pub mod adapter {
     /// // Building a new schedule/app...
     /// # use bevy_ecs::schedule::SystemStage;
     /// # let mut sched = Schedule::default(); sched
-    /// #     .add_stage(CoreStage::Update, SystemStage::single_threaded())
+    /// #     .add_stage(CoreStage::Update, SystemStage::parallel())
     ///     .add_system_to_stage(
     ///         CoreStage::Update,
     ///         // If the system fails, just move on and try again next frame.

crates/bevy_time/src/time.rs

@@ -120,7 +120,7 @@ impl Time {
     ///     world.insert_resource(time);
     ///     world.insert_resource(Health { health_value: 0.2 });
     ///
-    ///     let mut update_stage = SystemStage::single_threaded();
+    ///     let mut update_stage = SystemStage::parallel();
     ///     update_stage.add_system(health_system);
     ///
     ///     // Simulate that 30 ms have passed

crates/bevy_transform/src/systems.rs

@@ -320,7 +320,7 @@ mod test {
 
         // Adding the system in a single threaded stage. As the system will panic, this will
         // only bring down the current test thread.
-        app.add_stage("single", SystemStage::single_threaded())
+        app.add_stage("single", SystemStage::parallel())
             .add_system_to_stage("single", transform_propagate_system);
 
         fn setup_world(world: &mut World) -> (Entity, Entity) {