Update feature flags on dyn-star tests

Author: eholk

src/test/ui/async-await/dyn-star-trait-const.rs

@@ -1,5 +1,5 @@
 // run-pass
-#![feature(async_fn_in_traits)]
+#![feature(dyn_star)]
 #![allow(unused)]
 
 use std::fmt::Debug;

src/test/ui/async-await/dyn-star-trait-drop.rs

@@ -1,6 +1,6 @@
 // run-pass
 // check-run-results
-#![feature(async_fn_in_traits)]
+#![feature(dyn_star)]
 
 use std::fmt::Debug;
 

src/test/ui/async-await/dyn-star-trait-error.rs

@@ -1,4 +1,4 @@
-#![feature(async_fn_in_traits)]
+#![feature(dyn_star)]
 
 use std::fmt::Debug;
 

src/test/ui/async-await/dyn-star-trait-method.rs

@@ -1,5 +1,5 @@
 // run-pass
-#![feature(async_fn_in_traits)]
+#![feature(dyn_star)]
 
 trait Foo {
     fn get(&self) -> usize;