refactor(kernel,test_runner): remove #![feature(pin_macro)]

Author: yvt

src/r3_kernel/src/lib.rs

@@ -27,7 +27,6 @@
 #![feature(const_swap)]
 #![feature(never_type)] // `!`
 #![feature(decl_macro)]
-#![feature(pin_macro)]
 #![feature(doc_cfg)] // `#[doc(cfg(...))]`
 #![deny(unsafe_op_in_unsafe_fn)]
 #![cfg_attr(

src/r3_test_runner/src/main.rs

@@ -4,7 +4,6 @@
 #![feature(lint_reasons)]
 #![feature(decl_macro)] // `macro`
 #![feature(once_cell)]
-#![feature(pin_macro)] // `core::pin::pin!`
 #![warn(must_not_suspend)]
 use anyhow::{bail, Context};
 use clap::Parser;