MINOR: Add a missing @test to test case "shouldCallOldImplementationExceptionHandler" (apache#20427)

`shouldCallOldImplementationExceptionHandler` should be a test case, but
somehow misses the `@Test` tag

Reviewers: Ken Huang <[email protected]>, TaiJuWu <[email protected]>,
 Chia-Ping Tsai <[email protected]>

Author: frankvicky

streams/src/test/java/org/apache/kafka/streams/processor/internals/RecordCollectorTest.java

@@ -2008,6 +2008,7 @@ public void configure(final Map<String, ?> configs) {
         }
     }
 
+    @Test
     public void shouldCallOldImplementationExceptionHandler() {
         final KafkaException exception = new KafkaException("KABOOM!");
         final StreamsProducer streamProducer = getExceptionalStreamsProducerOnSend(exception);