Remove all uses of #[staged_api]

src/liballoc/lib.rs

@@ -60,7 +60,7 @@
 #![cfg_attr(stage0, feature(custom_attribute))]
 #![crate_name = "alloc"]
 #![crate_type = "rlib"]
-#![staged_api]
+#![cfg_attr(stage0, staged_api)]
 #![allow(unused_attributes)]
 #![unstable(feature = "alloc",
             reason = "this library is unlikely to be stabilized in its current \