OZG-3931 [test] fix sonar issue

mail-service/src/test/java/de/itvsh/ozg/mail/postfach/bayernid/BayernIdPostfachRemoteServiceTest.java

@@ -121,8 +121,9 @@ class BayernIdPostfachRemoteServiceTest {
 		void shouldThrowPostfachRuntimeException() {
 			when(webServiceTemplate.marshalSendAndReceive(any())).thenThrow(RuntimeException.class);
 
-			assertThatExceptionOfType(PostfachRuntimeException.class).isThrownBy(
-					() -> service.sendMessage(PostfachNachrichtTestFactory.create()));
+			var postfachNachricht = PostfachNachrichtTestFactory.create();
+
+			assertThatExceptionOfType(PostfachRuntimeException.class).isThrownBy(() -> service.sendMessage(postfachNachricht));
 		}
 
 		@Test