feature: api-151 validate webhook url with latest api

* Latest api uses simple string with regex pattern to validate webhook
* Because uri was conflicting with pattern
* So we can enable the validation test for webhook
* Still got a puzzling / weird requirement to import jakarta annotations though :(

Author: coling01

src/main/java/uk/gov/hmcts/cp/mappers/SubscriptionMapper.java

@@ -11,7 +11,6 @@
 import uk.gov.hmcts.cp.openapi.model.EventType;
 import uk.gov.hmcts.cp.openapi.model.NotificationEndpoint;
 
-import java.net.URI;
 import java.util.List;
 
 import static java.util.stream.Collectors.toList;