Change Readme to support ios 12

dotnet/ios/ios12/GroupedNotifications/README.md

@@ -37,11 +37,6 @@ by swiping down from the top of the device. You will see:
   thread, but iOS 12 by default groups together all app-related
   notifications not assigned to a specific thread)
 
-## Build Requirements
-
-iOS 14.0
-- UNNotificationPresentationOptions has some enums that were deprecated in iOS 14 and this sample uses the updated enums
-
 ## License
 
 Code is released under the MIT license