use slice::contains where applicable

compiler/rustc_span/src/lib.rs

@@ -876,7 +876,7 @@ impl Span {
         self.ctxt()
             .outer_expn_data()
             .allow_internal_unstable
-            .is_some_and(|features| features.iter().any(|&f| f == feature))
+            .is_some_and(|features| features.contains(&feature))
     }
 
     /// Checks if this span arises from a compiler desugaring of kind `kind`.