Remove the feature(const_fn_union) which is no longer needed.

sunfishcode · sunfishcode · commit 0e85369be17c · 2021-09-05T19:49:55.000-07:00
diff --git a/src/lib.rs b/src/lib.rs
@@ -45,7 +45,6 @@
 #![deny(missing_docs)]
 #![cfg_attr(linux_raw, deny(unsafe_code))]
 #![cfg_attr(linux_raw_inline_asm, feature(asm))]
-#![cfg_attr(const_fn_union, feature(const_fn_union))]
 #![cfg_attr(rustc_attrs, feature(rustc_attrs))]
 #![cfg_attr(target_os = "wasi", feature(wasi_ext))]
 #![cfg_attr(
