fix: remove #![feature(maybe_uninit_ref)]

yvt · yvt · commit 550be96bc63c · 2021-12-05T12:21:23.000+09:00
It's been stabilized by <rust-lang/rust#86273>.
diff --git a/src/r3_support_rp2040/src/lib.rs b/src/r3_support_rp2040/src/lib.rs
@@ -4,7 +4,6 @@
 //! [R3]: ::r3
 //! [Raspberry Pi Pico]: https://pico.raspberrypi.org
 #![feature(raw_ref_op)]
-#![feature(maybe_uninit_ref)]
 #![feature(asm)]
 #![feature(const_fn_trait_bound)]
 #![feature(const_mut_refs)]
