Don't rely on Debug impl for Erased

compiler/rustc_middle/src/query/erase.rs

@@ -1,21 +1,12 @@
 use crate::ty;
 use std::intrinsics::type_name;
-use std::{
-    fmt,
-    mem::{size_of, transmute_copy, MaybeUninit},
-};
+use std::mem::{size_of, transmute_copy, MaybeUninit};
 
 #[derive(Copy, Clone)]
 pub struct Erased<T: Copy> {
     data: MaybeUninit<T>,
 }
 
-impl<T: Copy> fmt::Debug for Erased<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "Erased")
-    }
-}
-
 pub trait EraseType: Copy {
     type Result: Copy;
 }