fix: update iterator and macro text for typos and clarity

- /macros/README.md: Typo "modules" => "macros"
- iterators2.py: Reduce line length to <90-char width.
- iterators4.py: Update 'fun' => 'challenge' as per PR#177
- rustlings hint iterators4: improve clarity

info.toml

@@ -640,10 +640,10 @@ name = "iterators4"
 path = "exercises/standard_library_types/iterators4.rs"
 mode = "test"
 hint = """
-In an imperative language you might write a for loop to iterate through
-multiply the values into a mutable variable. Or you might write code more
-functionally with recursion and a match clause. But you can also use ranges
-and iterators to solve this in rust."""
+In an imperative language, you might write a for loop that updates 
+a mutable variable. Or, you might write code utilizing recursion 
+and a match clause. In Rust you can take another functional
+approach, computing the factorial elegantly with ranges and iterators."""
 
 # TRAITS