Remove now-stable try_from feature

- The try_from feature was stabilized in #58302

Change-Id: I78540aa633a271ca977f8c40d05227f1987f8882
diff --git a/src/lib.rs b/src/lib.rs
index a58c679..b4e71e1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -46,11 +46,6 @@
 // just in case we forget to add #[forbid(unsafe_code)] on new module
 // definitions
 #![deny(unsafe_code)]
-// NOTE(joshlf): This is the only feature we allow. It keeps us from working on
-// stable Rust, but that's justified by the fact that it's important for
-// ensuring the soundness of our unsafe code. Once this feature is stabilized,
-// we will promise to work on stable going forward.
-#![feature(try_from)]
 
 #[macro_use]
 mod macros;