remove feature gate that is no longer used

Author: yotamofek

src/librustdoc/lib.rs

@@ -7,7 +7,6 @@
 #![feature(box_patterns)]
 #![feature(debug_closure_helpers)]
 #![feature(file_buffered)]
-#![feature(format_args_nl)]
 #![feature(if_let_guard)]
 #![feature(impl_trait_in_assoc_type)]
 #![feature(iter_intersperse)]