fix: align Turkish TDD test to expect NullPointerException

Objects.requireNonNull throws NullPointerException, not
IllegalArgumentException. The English source was correct;
the Turkish translation had the wrong exception type.

docs/tr/skills/quarkus-tdd/SKILL.md

@@ -442,8 +442,8 @@ class EventServiceTest {
       Object nullPayload = null;
       
       // ACT & ASSERT
-      IllegalArgumentException exception = assertThrows(
-          IllegalArgumentException.class,
+      NullPointerException exception = assertThrows(
+          NullPointerException.class,
           () -> eventService.createSuccessEvent(nullPayload, "EVENT_TYPE")
       );