message: chore(header): fix unused_unsafe in internals
diff: @@ -93,6 +93,10 @@ impl<V: ?Sized + Any + 'static> PtrMapCell<V> {
  #[inline]
  pub fn into_value(self, key: TypeId) -> Option<Box<V>> {
  + // UnsafeCell::into_inner was unsafe forever, and 1.25 has removed
  + // the unsafe modifier, resulting in a warning. This allow can be
  + // removed when the minimum supported rust version is at least 1.25.
  + #[allow(unused_unsafe)]
  let map = unsafe { self.0.into_inner() };
  match map {
  PtrMap::Empty => None,
  