chore: remove naked_functions cfg_attr

Stabilized starting from 1.88.

See:
- rust-lang/rust#134213
- https://releases.rs/docs/1.88.0/

Author: n0toose

rftrace/src/lib.rs

@@ -2,7 +2,6 @@
 //! Provides an `mcount` implementation, which does nothing by default but can be enabled via frontend.
 //! A lot of documentation can be found in the parent workspaces [readme](https://github.com/hermit-os/rftrace).
 
-#![cfg_attr(feature = "staticlib", feature(naked_functions))]
 #![cfg_attr(feature = "staticlib", feature(thread_local))]
 #![cfg_attr(feature = "staticlib", no_std)]