Remove vestigial reference to UIActionSheetDelegate (facebook#41402)

Summary:
Pull Request resolved: facebook#41402

Changelog: [Internal]

UIActionSheet was deprecated in iOS 8.3.

The RCTActionSheetManager class listed the UIActionSheetDelegate as an adopted protocol but none of the protocol methods were implemented.

Reviewed By: sammy-SC

Differential Revision: D50732844

fbshipit-source-id: e954f1e9a03e80561b3b066557e56c7f3d3589d4

packages/react-native/React/CoreModules/RCTActionSheetManager.mm

@@ -20,7 +20,7 @@
 
 using namespace facebook::react;
 
-@interface RCTActionSheetManager () <UIActionSheetDelegate, NativeActionSheetManagerSpec>
+@interface RCTActionSheetManager () <NativeActionSheetManagerSpec>
 
 @property (nonatomic, strong) NSMutableArray<UIAlertController *> *alertControllers;