remove no longer necessary allows

src/arena.rs

@@ -1,6 +1,3 @@
-#![allow(clippy::new_without_default)] // annotating structs annotated with #[bitfield] doesn't work
-#![allow(unused_parens)] // see mthom/scryer-prolog#3092 and rust-lang/rust#147126
-
 #[cfg(feature = "http")]
 use crate::http::{HttpListener, HttpResponse};
 use crate::machine::heap::AllocError;