update fifth-extras

Signed-off-by: husharp <jinhao.hu@pingcap.com>

src/too-many-lists/unsafe-queue/extra-junk.md

@@ -141,22 +141,26 @@ impl<'a, T> Iterator for Iter<'a, T> {
     type Item = &'a T;
 
     fn next(&mut self) -> Option<Self::Item> {
+        unsafe {
             self.next.map(|node| {
-            self.next = node.next.as_deref();
+                self.next = node.next.as_ref();
                 &node.elem
             })
         }
+    }
 }
 
 impl<'a, T> Iterator for IterMut<'a, T> {
     type Item = &'a mut T;
 
     fn next(&mut self) -> Option<Self::Item> {
+        unsafe {
             self.next.take().map(|node| {
-            self.next = node.next.as_deref_mut();
+                self.next = node.next.as_mut();
                 &mut node.elem
             })
         }
+    }
 }
 ```