fix(primitive_types4): update outdated hint

Exercise was changed to test (and the order was switched) in rust-lang#209.

info.toml

@@ -152,8 +152,8 @@ https://doc.rust-lang.org/book/ch04-03-slices.html
 and use the starting and ending indices of the items in the Array
 that you want to end up in the slice.
 
-If you're curious why the right hand of the `==` comparison does not
-have an ampersand for a reference since the left hand side is a
+If you're curious why the first argument of `assert_eq!` does not
+have an ampersand for a reference since the second argument is a
 reference, take a look at the Deref coercions section of the book:
 https://doc.rust-lang.org/book/ch15-02-deref.html"""