fix example tests

Now that the first SLI example opens a GUI window we need to skip it on JVMs >= 8.

Author: mtf90

examples/src/test/java/de/learnlib/examples/ExamplesTest.java

@@ -89,6 +89,7 @@ public void testPassiveExample1() {
 
     @Test
     public void testSLIExample1() {
+        checkJVMCompatibility();
         de.learnlib.examples.sli.Example1.main(new String[0]);
     }