Remove unneeded features.

compiler/rustc_ast_pretty/src/lib.rs

@@ -3,9 +3,7 @@
 #![doc(rust_logo)]
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
-#![feature(associated_type_bounds)]
 #![feature(box_patterns)]
-#![feature(with_negative_coherence)]
 #![recursion_limit = "256"]
 
 mod helpers;