chore(content/til): update "2024_02_07-iter_vs_into__iter"

content/til/2024_02_07-iter_vs_into__iter.mdx

@@ -83,3 +83,5 @@ So:
 `into_iter` is a generic method to obtain an iterator, whether this iterator yields values, immutable references or mutable references **is context dependent** and can sometimes be surprising.
 
 `iter` and `iter_mut` are ad-hoc methods. Their return type is therefore independent of the context, and will conventionally be iterators yielding immutable references and mutable references, respectively.
+
+**ref:** https://stackoverflow.com/a/34745885