Add missing @Test annotation (ReactiveX#6990)

Author: BraisGabin

src/test/java/io/reactivex/rxjava3/subjects/ReplaySubjectTest.java

@@ -797,6 +797,7 @@ public void getValuesUnbounded() {
 
     }
 
+    @Test
     public void createInvalidCapacity() {
         try {
             ReplaySubject.create(-99);