message: Update example for new interface of MaybeUninit.
diff: @@ -260,7 +260,7 @@ impl<T> Drop for OptionCell<T> {
  if self.is_init {
  // Safety: `value` is guaranteed to be fully initialized when `is_init` is true.
  // Safety: The cell is being dropped, so it can't be accessed again.
  - drop(unsafe { self.value.read() });
  + unsafe { self.value.assume_init_drop() };
  }
  }
  }
  