Clean up E0730 explanation

Author: GuillaumeGomez

src/librustc_error_codes/error_codes/E0730.md

@@ -1,6 +1,6 @@
 An array without a fixed length was pattern-matched.
 
-Example of erroneous code:
+Erroneous code example:
 
 ```compile_fail,E0730
 #![feature(const_generics)]
@@ -14,8 +14,8 @@ fn is_123<const N: usize>(x: [u32; N]) -> bool {
 }
 ```
 
-Ensure that the pattern is consistent with the size of the matched
-array. Additional elements can be matched with `..`:
+Ensure that the pattern is consistent with the size of the matched array.
+Additional elements can be matched with `..`:
 
 ```
 let r = &[1, 2, 3, 4];