Update tests for hidden references to mutable static

Author: obeis

library/alloc/src/collections/linked_list/tests.rs

@@ -1,3 +1,6 @@
+// FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
+#![allow(static_mut_refs)]
+
 use std::panic::{catch_unwind, AssertUnwindSafe};
 use std::thread;
 

library/alloc/src/collections/vec_deque/tests.rs

@@ -1,3 +1,6 @@
+// FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
+#![allow(static_mut_refs)]
+
 use core::iter::TrustedLen;
 
 use super::*;