Revert change to assertion message

Author: balt-dev

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

@@ -2102,11 +2102,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     #[track_caller]
     #[must_use = "if you don't need a reference to the value, use VecDeque::insert instead"]
     pub fn insert_mut(&mut self, index: usize, value: T) -> &mut T {
-        assert!(
-            index <= self.len,
-            "insertion index (is {index}) should be <= len (is {})",
-            self.len()
-        );
+        assert!(index <= self.len(), "index out of bounds");
 
         if self.is_full() {
             self.grow();