Fix Swift example links on top-level README
Fix Swift example links on top-level README

ya7lelkom/googleads-mobile-ios-examples,googleads/googleads-mobile-ios-examples,ya7lelkom/googleads-mobile-ios-examples,JeremyPacker/googleads-mobile-ios-examples,googleads/googleads-mobile-ios-examples,googleads/googleads-mobile-ios-examples,JeremyPacker/googleads-mobile-ios-examples,a20251313/googleads-mobile-ios-examples,a20251313/googleads-mobile-ios-examples