fix(rustup): str.split and associated type changes

src/header/mod.rs

@@ -645,7 +645,7 @@ mod tests {
 
         let s = headers.to_string();
         // hashmap's iterators have arbitrary order, so we must sort first
-        let mut pieces = s.split_str("\r\n").collect::<Vec<&str>>();
+        let mut pieces = s.split("\r\n").collect::<Vec<&str>>();
         pieces.sort();
         let s = pieces.into_iter().rev().collect::<Vec<&str>>().connect("\r\n");
         assert_eq!(s, "Host: foo.bar\r\nContent-Length: 15\r\n");