[Ink] Add nonnull to the MDCInkTouchController initializer (#1123)

* Specify `nonnull` on the MDCInkTouchController initializer.

This is a quick change since the initializer was never returning nil to begin with.

* Update Shrine to use the nonnull MDCInkTouchController initializer.

Author: samsymons

catalog/MDCCatalog/MDCCatalogComponentsController.swift

@@ -71,7 +71,7 @@ class MDCCatalogComponentsController: UICollectionViewController, MDCInkTouchCon
   override func viewDidLoad() {
     super.viewDidLoad()
 
-    inkController = MDCInkTouchController(view: self.collectionView!)!
+    inkController = MDCInkTouchController(view: self.collectionView!)
     inkController!.addInkView()
     inkController!.delaysInkSpread = true
     inkController!.delegate = self

components/Ink/src/MDCInkTouchController.h

@@ -81,7 +81,7 @@
 
  @param view View that responds to touch events for ink.
  */
-- (nullable instancetype)initWithView:(nonnull UIView *)view NS_DESIGNATED_INITIALIZER;
+- (nonnull instancetype)initWithView:(nonnull UIView *)view NS_DESIGNATED_INITIALIZER;
 
 /**
  When called the @c defaultInkView is added to the @c view.

demos/Shrine/Shrine/ShrineInkOverlay.swift

@@ -24,7 +24,7 @@ class ShrineInkOverlay: UIView, MDCInkTouchControllerDelegate {
   override init(frame: CGRect) {
     super.init(frame: frame)
     let cyan = UIColor(red: 22 / 255, green: 240 / 255, blue: 240 / 255, alpha: 0.2)
-    self.inkTouchController = MDCInkTouchController(view:self)!
+    self.inkTouchController = MDCInkTouchController(view:self)
     self.inkTouchController!.defaultInkView.inkColor = cyan
     self.inkTouchController!.addInkView()
     self.inkTouchController!.delegate = self