simplify Factory::de (typeless)

src/rstd/typeless.rs

@@ -131,7 +131,7 @@ where
         'a: 'c,
     {
         self.deserialize(demoted)
-            .map_err(|e| Box::new(e) as Box<dyn 'a + Error>)
+            .map_err(|e| Box::new(e) as _)
             .map(Rc::new)
             .map(TypelessMentionable::from_typed)
     }