Update 2012-08-13-nsincrementalstore.md

Fixed return type of `-executeRequest:withContext:error:` if `resultType` is `NSCountResultType` from `NSNumber` to `NSArray` containing a `NSNumber`.

[Source](http://developer.apple.com/library/ios/documentation/CoreData/Reference/NSIncrementalStore_Class/Reference/NSIncrementalStore.html#//apple_ref/occ/instm/NSIncrementalStore/executeRequest:withContext:error:)