minor refactor: tweak cherry-picked statement for JDK 8

Author: paulk-asert

src/test/groovy/org/codehaus/groovy/reflection/SecurityTest.java

@@ -35,7 +35,7 @@
 
 public class SecurityTest extends GroovyTestCase {
 
-    private final boolean skip = Runtime.version().feature() >= 24;
+    private final boolean skip = isAtLeastJdk("24");
 
     @SuppressWarnings("unused")
     public class TestClass{