Scheduler lock-up when combining `after` and `chain()`

## Bevy version

0.12.1 (-F dynamic_linking)

## What you did

Source code (36 lines)

```rust
#![allow(clippy::needless_pass_by_value)]
use bevy::prelude::*;

#[derive(Resource)]
pub struct MyTimer(pub Timer);

fn fn_a(time: Res, mut timer: ResMut) {
println!("a called");
if timer.0.tick(time.delta()).just_finished() {
println!("a works");
}
}

fn fn_b(mut commands: Commands, timer: ResMut) {
println!("b called");
if !timer.0.just_finished() {
return;
}
println!("b works");
}

fn main() {
App::new()
.add_plugins(DefaultPlugins)
.insert_resource(MyTimer(Timer::from_seconds(0.2, TimerMode::Repeating)))
.add_systems(
Update,
(
apply_deferred.after(fn_a), // this line causes a lockup
// fn_a, // uncomment these lines
// apply_deferred, // and it will run properly
fn_b,
)
.chain(),
)
.run();
}
```

## What went wrong

System `fn_a` is never run (and therefore never frees up the timer for b to perform work - even though b is run)