Revert "Temporarily suppress where_clauses_object_safety due to regression"

This reverts commit 922699e.

Author: dtolnay

tests/test.rs

@@ -10,9 +10,6 @@
     clippy::trivially_copy_pass_by_ref,
     clippy::unused_async
 )]
-// Temporarily suppressed due to rustc regression.
-// https://github.com/rust-lang/rust/issues/106247
-#![allow(where_clauses_object_safety)]
 
 use async_trait::async_trait;