Revert "Add ThemeService nullability annotations"

This reverts commit dacb3b1.

Author: kean

WordPress/Classes/Services/ThemeService.h

@@ -1,14 +1,12 @@
 #import "CoreDataStack.h"
 
-NS_ASSUME_NONNULL_BEGIN
-
 @class Blog;
 @class Theme;
 @class WPAccount;
 
 typedef void(^ThemeServiceSuccessBlock)(void);
-typedef void(^ThemeServiceThemeRequestSuccessBlock)(Theme * _Nullable theme);
-typedef void(^ThemeServiceThemesRequestSuccessBlock)(NSArray<Theme *> * _Nullable themes, BOOL hasMore, NSInteger totalThemeCount);
+typedef void(^ThemeServiceThemeRequestSuccessBlock)(Theme *theme);
+typedef void(^ThemeServiceThemesRequestSuccessBlock)(NSArray<Theme *> *themes, BOOL hasMore, NSInteger totalThemeCount);
 typedef void(^ThemeServiceFailureBlock)(NSError *error);
 
 @interface ThemeService : NSObject
@@ -112,5 +110,3 @@ typedef void(^ThemeServiceFailureBlock)(NSError *error);
 
 
 @end
-
-NS_ASSUME_NONNULL_END