Update src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-no-fg.rs

Co-Authored-By: matthewjasper <mjjasper1@gmail.com>

Author: nikomatsakis

src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-no-fg.rs

@@ -3,7 +3,7 @@
 // Test that a feature gate is needed to use `impl Trait` as the
 // return type of an async.
 
-#![feature(arbitrary_self_types, async_await, await_macro)]
+#![feature(async_await)]
 
 trait Trait<'a, 'b> { }
 impl<T> Trait<'_, '_> for T { }