SegmentedCell: cast row to OptionsRow not to the SegmentedRow

[maxisa2017]

SegmentedCell can only be used with SegmentedRow. It force-casts the row value to SegmentedRow when it reads an options variable. Actually this var is a part of OptionsProviderRow protocol.
Changing the casting type to OptionsRow allows us to keep the same behaviour for existing classes and extends the reuse of SegmentedCell.
We cannot modify SegmentedRow class, because it is marked as final, but we will be able to use this cell in custom classes:

// MARK: AdvancedSegmentedRow
public final class AdvancedSegmentedRow<T: Equatable>: OptionsRow<SegmentedCell<T>>, RowType {
  required public init(tag: String?) {
    super.init(tag: tag)
  }

public override func updateCell() {
    super.updateCell()
    cell.applyDisabledAppearance()
  }
}