Fix a typo in the explanation of E0588

Author: LingMan

compiler/rustc_error_codes/src/error_codes/E0588.md

@@ -11,7 +11,7 @@ struct Aligned(i32);
 struct Packed(Aligned);
 ```
 
-Just like you cannot have both `align` and `packed` representation hints on a
+Just like you cannot have both `align` and `packed` representation hints on the
 same type, a `packed` type cannot contain another type with the `align`
 representation hint. However, you can do the opposite: