rust: remove try_reserve feature

It is enabled by default as of Rust 1.57.

Author: indygreg

rust-ext/src/lib.rs

@@ -4,8 +4,6 @@
 // This software may be modified and distributed under the terms
 // of the BSD license. See the LICENSE file for details.
 
-#![feature(try_reserve)]
-
 use pyo3::{prelude::*, types::PySet};
 
 mod buffers;