title: removal of spacing between specific UICollectionViewCells
body: <p>I am using <code>UICollectionFlowLayout</code> to establish <code>minimumLineSpacing</code> between collectionItems, I am trying to find a way to set the spacing to zero for some cells so there is no spacing, i.e they appear to be 'merged' while leaving others with their spaces intact, is it possible to make alterations in the <code>cellForItemAt</code> method for example to achieve this?</p>
  
  <pre><code>func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -&gt; UICollectionViewCell {
       let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "customColCell", for: indexPath) as! customColCell
  
       if indexPath.row == 5 {
          self.minimumLineSpacing = 100 // -- this does not result in an individual change...
       }
  
       cell.textLabel.text = indexPath.row.description
       return cell
  }
  </code></pre>