fix: doc generation error caused by duplicated portable_simd (#327)

* sync: return error if doc generation fail

* fix: doc generation error caused by duplicated `#![feature(portable_simd)]`

Author: Marsman1996

dv

@@ -25,7 +25,6 @@
 #![feature(proc_macro_hygiene)]
 #![allow(unused_parens)]
 #![allow(unused_braces)]
-#![feature(portable_simd)]
 #![allow(rustdoc::invalid_rust_codeblocks)]
 #![allow(rustdoc::invalid_html_tags)]
 #![allow(rustdoc::broken_intra_doc_links)]