doc: this statement does not have an effect

Author: tshepang

src/libcollections/fmt.rs

@@ -292,8 +292,6 @@
 //! use std::fmt;
 //! use std::io::{self, Write};
 //!
-//! fmt::format(format_args!("this returns {}", "String"));
-//!
 //! let mut some_writer = io::stdout();
 //! write!(&mut some_writer, "{}", format_args!("print with a {}", "macro"));
 //!