Fix `const_fn` feature gate rename (`const_fn_trait_bounds`)

Fortune for smallmap's current commit: Future small blessing − 末小吉

Cargo.toml

@@ -4,7 +4,7 @@ description = "Small byte-sized generic key-value map type"
 keywords = ["map", "table", "small", "key", "value"]
 repository = "https://github.com/notflan/smallmap"
 homepage= "https://git.flanchan.moe/flanchan/smallmap"
-version = "1.3.0"
+version = "1.3.1"
 authors = ["Avril <flanchan@cumallover.me>"]
 edition = "2018"
 license = "MIT"

src/lib.rs

@@ -29,7 +29,7 @@
 
 #![cfg_attr(nightly, feature(test))] 
 #![cfg_attr(nightly, feature(drain_filter))] 
-#![cfg_attr(nightly, feature(const_fn))] 
+#![cfg_attr(nightly, feature(const_fn_trait_bound))] 
 #![cfg_attr(nightly, feature(never_type))] 
 
 #[cfg(nightly)] extern crate test;