Clean up E0754 explanation

Author: GuillaumeGomez

src/librustc_error_codes/error_codes/E0754.md

@@ -1,31 +1,27 @@
 An non-ascii identifier was used in an invalid context.
 
-Erroneous code example:
+Erroneous code examples:
 
 ```compile_fail,E0754
 # #![feature(non_ascii_idents)]
 
 mod řųśť;
 // ^ error!
-fn main() {}
-```
-
-```compile_fail,E0754
-# #![feature(non_ascii_idents)]
 
 #[no_mangle]
 fn řųśť() {}
 // ^ error!
+
 fn main() {}
 ```
 
-Non-ascii can be used as module names if it is inline
-or a #\[path\] attribute is specified. For example:
+Non-ascii can be used as module names if it is inline or a `#[path]` attribute
+is specified. For example:
 
 ```
 # #![feature(non_ascii_idents)]
 
-mod řųśť {
+mod řųśť { // ok!
     const IS_GREAT: bool = true;
 }