[fixup] fix build failure in config_proc_macro

Author: tommilligan

config_proc_macro/Cargo.lock

@@ -1,7 +1,7 @@
 pub mod config {
     pub trait ConfigType: Sized {
         fn doc_hint() -> String;
-        fn stable_variant(&self, nightly: bool) -> bool;
+        fn stable_variant(&self) -> bool;
     }
 }