Remove vertical space between UICollectionViewCell

Code Block 
class ViewController: UIViewController {
		
		override func viewDidLoad() {
				super.viewDidLoad()
				let collection = ColorCollectionView(sectionHeadersPinToVisibleBounds: false)
				self.view.addSubview(collection)
				collection.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 8).isActive = true
				collection.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 8).isActive = true
				collection.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -8).isActive	= true
				collection.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -8).isActive	= true
				collection.translatesAutoresizingMaskIntoConstraints = false
				
				let colors: [UIColor] = [.systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,
																 .systemGray, .systemGray2, .systemGray3,]
				collection.colors = colors
		}
}
class ColorCollectionView: UICollectionView {
		var colors: [UIColor] = []
		
		var selectedColor: UIColor?
		
		var headerName: String?
		
		override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout) {
				super.init(frame: frame, collectionViewLayout: layout)
				self.backgroundColor = .clear
				self.register(ColorCollectionViewCell.self, forCellWithReuseIdentifier:ColorCollectionViewCell.identifier)
				self.dataSource = self
				self.delegate = self
		}
		
		convenience init(sectionHeadersPinToVisibleBounds: Bool) {
				let layout = UICollectionViewFlowLayout()
				layout.sectionHeadersPinToVisibleBounds = sectionHeadersPinToVisibleBounds
				layout.scrollDirection = .vertical
				self.init(frame: .zero,	collectionViewLayout: layout)
				
		}
		
		required init?(coder aDecoder: NSCoder) {
				fatalError("init(coder:) has not been implemented")
		}
}
extension ColorCollectionView: UICollectionViewDelegateFlowLayout {
		
		func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
				return CGSize(width: collectionView.frame.width / 3, height: 60)
		}
		
		func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout,
												minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
				return CGFloat.leastNormalMagnitude
		}
		func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
				return 8
		}
}
extension ColorCollectionView: UICollectionViewDataSource {
		func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
				return colors.count
		}
		
		func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
				let cell = collectionView.dequeueReusableCell(withReuseIdentifier: ColorCollectionViewCell.identifier, for: indexPath)
				let color = colors[indexPath.row]
				cell.backgroundColor = color
				return cell
		}
}
class ColorCollectionViewCell: UICollectionViewCell {
		static let identifier = "ColorCollectionViewCell"
}

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