Remove potentially unsound note on reconstructing a leaked Vec.

library/alloc/src/vec/mod.rs

@@ -1955,9 +1955,6 @@ impl<T, A: Allocator> Vec<T, A> {
     /// As of Rust 1.57, this method does not reallocate or shrink the `Vec`,
     /// so the leaked allocation may include unused capacity that is not part
     /// of the returned slice.
-    /// Unsafe code that later reconstructs or deallocates the `Vec` (for
-    /// example, by calling [`Vec::from_raw_parts`]) must keep track of the
-    /// original capacity.
     ///
     /// This function is mainly useful for data that lives for the remainder of
     /// the program's life. Dropping the returned reference will cause a memory