Style: Change order and visibility of nested class to private

src/test/java/ch/unibas/dmi/dbis/cs108/casono/server/network/events/EventBusTest.java

@@ -10,13 +10,13 @@ import org.junit.jupiter.api.Test;
 public class EventBusTest {
     private EventBus eventBus;
 
+    private class TestEvent implements Event {}
+
     @BeforeEach
     void setUp() {
         eventBus = new EventBus();
     }
 
-    static class TestEvent implements Event {}
-
     @Test
     void testSingleSubscriberReceivesEvent() {
         AtomicBoolean called = new AtomicBoolean(false);