Auto merge of #81312 - dylni:clarify-btree-range-search-comments, r=m-ou-se

Clarify BTree `range_search` comments

These comments were added by #81169. However, the soundness issue [might not be exploitable here](https://github.com/rust-lang/rust/pull/81169#issuecomment-765271717), so the comments should be updated.

cc `@ssomers`

library/alloc/src/collections/btree/search.rs

@@ -94,9 +94,8 @@ impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Lea
         K: Borrow<Q>,
         R: RangeBounds<Q>,
     {
-        // WARNING: Inlining these variables would be unsound (#81138)
-        // We assume the bounds reported by `range` remain the same, but
-        // an adversarial implementation could change between calls
+        // Inlining these variables should be avoided. We assume the bounds reported by `range`
+        // remain the same, but an adversarial implementation could change between calls (#81138).
         let (start, end) = (range.start_bound(), range.end_bound());
         match (start, end) {
             (Bound::Excluded(s), Bound::Excluded(e)) if s == e => {