Remove unnecessary deallocator in RCTSliderComponentView

Summary:
Changelog: [Internal]

There is no need for custom dealloc, let's get rid of it.
We also prefer east const over west const.

Reviewed By: shergin

Differential Revision: D21997545

fbshipit-source-id: aa017f99aa26421fc59b353d0012687cb38fac08

React/Fabric/Mounting/ComponentViews/Slider/RCTSliderComponentView.mm

@@ -29,10 +29,10 @@ using namespace facebook::react;
   UIImage *_maximumTrackImage;
   UIImage *_thumbImage;
 
-  const ImageResponseObserverCoordinator *_trackImageCoordinator;
-  const ImageResponseObserverCoordinator *_minimumTrackImageCoordinator;
-  const ImageResponseObserverCoordinator *_maximumTrackImageCoordinator;
-  const ImageResponseObserverCoordinator *_thumbImageCoordinator;
+  ImageResponseObserverCoordinator const *_trackImageCoordinator;
+  ImageResponseObserverCoordinator const *_minimumTrackImageCoordinator;
+  ImageResponseObserverCoordinator const *_maximumTrackImageCoordinator;
+  ImageResponseObserverCoordinator const *_thumbImageCoordinator;
 
   RCTImageResponseObserverProxy _trackImageResponseObserverProxy;
   RCTImageResponseObserverProxy _minimumTrackImageResponseObserverProxy;
@@ -96,14 +96,6 @@ using namespace facebook::react;
   _previousValue = props.value;
 }
 
-- (void)dealloc
-{
-  self.trackImageCoordinator = nullptr;
-  self.minimumTrackImageCoordinator = nullptr;
-  self.maximumTrackImageCoordinator = nullptr;
-  self.thumbImageCoordinator = nullptr;
-}
-
 #pragma mark - RCTComponentViewProtocol
 
 + (ComponentDescriptorProvider)componentDescriptorProvider