removed more uses of feature gate

src/test/ui/borrowck/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs

@@ -1,5 +1,4 @@
 // Tests using a combination of pattern features has the expected borrow checking behavior
-#![feature(bindings_after_at)]
 #![feature(box_patterns)]
 
 enum Test {

src/test/ui/drop/dynamic-drop.rs

@@ -2,7 +2,6 @@
 // ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(generators, generator_trait)]
-#![feature(bindings_after_at)]
 
 #![allow(unused_assignments)]
 #![allow(unused_variables)]

src/test/ui/pattern/move-ref-patterns/by-move-sub-pat-unreachable.rs

@@ -4,8 +4,6 @@
 
 // check-pass
 
-#![feature(bindings_after_at)]
-
 fn main() {
     return;