DATAREST-1014 - Avoid Java 8 API usage in AnnotatedEventHandlerInvoker.

Dropped the call to Method.getParameterCount() in favor of ….getParameterTypes().length as the former method was introduced in Java 8.

spring-data-rest-core/src/main/java/org/springframework/data/rest/core/event/AnnotatedEventHandlerInvoker.java

@@ -166,7 +166,7 @@ public class AnnotatedEventHandlerInvoker implements ApplicationListener<Reposit
 			return;
 		}
 
-		if (method.getParameterCount() == 0) {
+		if (method.getParameterTypes().length == 0) {
 			throw new IllegalStateException(String.format(PARAMETER_MISSING, method));
 		}