Remove redundant #![feature(...)] 's from compiler/

compiler/rustc_middle/src/lib.rs

@@ -30,12 +30,9 @@
 #![feature(cmp_min_max_by)]
 #![feature(const_fn)]
 #![feature(const_panic)]
-#![feature(const_fn_transmute)]
 #![feature(core_intrinsics)]
 #![feature(discriminant_kind)]
-#![feature(drain_filter)]
 #![feature(never_type)]
-#![feature(exhaustive_patterns)]
 #![feature(extern_types)]
 #![feature(nll)]
 #![feature(once_cell)]
@@ -43,13 +40,11 @@
 #![feature(or_patterns)]
 #![feature(min_specialization)]
 #![feature(trusted_len)]
-#![feature(stmt_expr_attributes)]
 #![feature(test)]
 #![feature(in_band_lifetimes)]
 #![feature(crate_visibility_modifier)]
 #![feature(associated_type_bounds)]
 #![feature(rustc_attrs)]
-#![feature(hash_raw_entry)]
 #![feature(int_error_matching)]
 #![recursion_limit = "512"]