Added NS_UNAVAILABLE to new/init

Summary:
Not sure what was expected for a "designated initialiser" feel free to school me and I'll do it!

(Also just had to google difference between + and - in ObjC)

Issue fixed: #654, #652
Closes https://github.com/Instagram/IGListKit/pull/662

Differential Revision: D4900092

Pulled By: jessesquires

fbshipit-source-id: 7858065ecc88a9ad7cb064811f0180d0f84f174d

Source/Internal/IGListAdapterProxy.h

@@ -33,7 +33,17 @@ IGLK_SUBCLASSING_RESTRICTED
  */
 - (instancetype)initWithCollectionViewTarget:(nullable id<UICollectionViewDelegate>)collectionViewTarget
                             scrollViewTarget:(nullable id<UIScrollViewDelegate>)scrollViewTarget
-                                 interceptor:(IGListAdapter *)interceptor;
+                                 interceptor:(IGListAdapter *)interceptor NS_DESIGNATED_INITIALIZER;
+
+/**
+ :nodoc:
+ */
+- (instancetype)init NS_UNAVAILABLE;
+
+/**
+ :nodoc:
+ */
++ (instancetype)new NS_UNAVAILABLE;
 
 @end
 

Source/Internal/IGListSectionMap.h

@@ -107,6 +107,11 @@ IGLK_SUBCLASSING_RESTRICTED
  */
 - (instancetype)init NS_UNAVAILABLE;
 
+/**
+ :nodoc:
+ */
++ (instancetype)new NS_UNAVAILABLE;
+
 @end
 
 NS_ASSUME_NONNULL_END