chore: update line reference in strings2 hint

Author: willhack

info.toml

@@ -439,7 +439,7 @@ mode = "compile"
 hint = """
 Yes, it would be really easy to fix this by just changing the value bound to `word` to be a
 string slice instead of a `String`, wouldn't it?? There is a way to add one character to line
-9, though, that will coerce the `String` into a string slice.
+12, though, that will coerce the `String` into a string slice.
 
 Side note: If you're interested in learning about how this kind of reference conversion works, you can jump ahead in the book and read this part in the smart pointers chapter: https://doc.rust-lang.org/stable/book/ch15-02-deref.html#implicit-deref-coercions-with-functions-and-methods"""