Add missing @test annotation (#4359)

Author: dimitar-asenov

src/test/java/rx/ObservableTests.java

@@ -152,6 +152,7 @@ public void call(Subscriber<? super String> obsv) {
         verify(w, times(1)).onError(any(RuntimeException.class));
     }
 
+    @Test
     public void testTakeFirstWithPredicateOfSome() {
         Observable<Integer> observable = Observable.just(1, 3, 5, 4, 6, 3);
         observable.takeFirst(IS_EVEN).subscribe(w);