Clean up E0075 long explanation

Author: GuillaumeGomez

src/librustc_error_codes/error_codes/E0075.md

@@ -1,21 +1,23 @@
-The `#[simd]` attribute can only be applied to non empty tuple structs, because
-it doesn't make sense to try to use SIMD operations when there are no values to
-operate on.
+A `#[simd]` attribute was applied to an empty tuple struct.
 
-This will cause an error:
+Erroneous code example:
 
 ```compile_fail,E0075
 #![feature(repr_simd)]
 
 #[repr(simd)]
-struct Bad;
+struct Bad; // error!
 ```
 
-This will not:
+The `#[simd]` attribute can only be applied to non empty tuple structs, because
+it doesn't make sense to try to use SIMD operations when there are no values to
+operate on.
+
+Fixed example:
 
 ```
 #![feature(repr_simd)]
 
 #[repr(simd)]
-struct Good(u32);
+struct Good(u32); // ok!
 ```