fix(iterators2): Remove syntax resulting in misleading error message

closes #199

exercises/standard_library_types/iterators2.rs

@@ -9,7 +9,7 @@ pub fn capitalize_first(input: &str) -> String {
     let mut c = input.chars();
     match c.next() {
         None => String::new(),
-        Some(first) => first.collect()::<String>() + c.as_str(),
+        Some(first) => first.collect::<String>() + c.as_str(),
     }
 }