update unit tests

Author: Thomas Nield

src/test/java/io/reactivex/rxjavafx/sources/JavaFxObservableTest.java

@@ -36,11 +36,6 @@
 
 public final class JavaFxObservableTest {
 
-    @BeforeClass
-    public static void initJFX() {
-        javafx.application.Platform.startup(() ->{});
-    }
-
     @Test
     public void testIntervalSource() {