Rollup merge of rust-lang#70188 - GuillaumeGomez:cleanup-e0439, r=Dylan-DPC

Clean up E0439 explanation

r? @Dylan-DPC

Author: Centril

src/librustc_error_codes/error_codes/E0439.md

@@ -1,5 +1,6 @@
-The length of the platform-intrinsic function `simd_shuffle`
-wasn't specified. Erroneous code example:
+The length of the platform-intrinsic function `simd_shuffle` wasn't specified.
+
+Erroneous code example:
 
 ```compile_fail,E0439
 #![feature(platform_intrinsics)]