ci: use beta, add secondary nightly ci.

docs/modules/ROOT/examples/basic/src/main.rs

@@ -1,6 +1,5 @@
 #![no_std]
 #![no_main]
-#![feature(type_alias_impl_trait)]
 
 use defmt::*;
 use embassy_executor::Spawner;

docs/modules/ROOT/examples/layer-by-layer/blinky-async/Cargo.toml

@@ -8,7 +8,7 @@ license = "MIT OR Apache-2.0"
 cortex-m = "0.7"
 cortex-m-rt = "0.7"
 embassy-stm32 = { version = "0.1.0", features = ["stm32l475vg", "memory-x", "exti"]  }
-embassy-executor = { version = "0.4.0", features = ["nightly", "arch-cortex-m", "executor-thread"] }
+embassy-executor = { version = "0.4.0", features = ["arch-cortex-m", "executor-thread"] }
 
 defmt = "0.3.0"
 defmt-rtt = "0.3.0"

docs/modules/ROOT/examples/layer-by-layer/blinky-async/src/main.rs

@@ -1,6 +1,5 @@
 #![no_std]
 #![no_main]
-#![feature(type_alias_impl_trait)]
 
 use embassy_executor::Spawner;
 use embassy_stm32::exti::ExtiInput;