Remove #[macro_use] extern crate tracing from rustc_const_eval.

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -8,6 +8,7 @@ use std::fmt::Write;
 use std::num::NonZero;
 
 use either::{Left, Right};
+use tracing::trace;
 
 use hir::def::DefKind;
 use rustc_ast::Mutability;