Exclude HTMLUnit failing assertion in Jenkins 2.400 and later

jenkinsci/bom#1959 (comment)
explains that the modernization of hetero-list.js has inserted JavaScript
that the HTMLUnit JavaScript engine does not understand.  That causes
the test to fail with an HTTP 500 error when the specific assertion
is executed.

Do not execute the failing assertion on Jenkins 2.400 and
later.  Excluding the failing assertion is a simple short-term
workaround for the larger problem that is described by @basil in
jenkinsci/jenkins-test-harness#569 (comment)

src/test/java/org/jenkinsci/plugins/workflow/libs/LibraryStepTest.java

@@ -33,6 +33,7 @@
 import hudson.plugins.git.SubmoduleConfig;
 import hudson.plugins.git.UserRemoteConfig;
 import hudson.plugins.git.extensions.GitSCMExtension;
+import hudson.util.VersionNumber;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
@@ -77,7 +78,10 @@ public class LibraryStepTest {
         scmSource.setCredentialsId(""); // TODO the setter ought to use fixEmpty
         s.setRetriever(new SCMSourceRetriever(scmSource));
         s.setChangelog(true);
-        r.assertEqualDataBoundBeans(s, stepTester.configRoundTrip(s));
+        // TODO Assertion fails with 2.400 and later due to outdated JavaScript support in HTMLUnit
+        if (r.jenkins.get().getVersion().isOlderThan(new VersionNumber("2.400"))) {
+            r.assertEqualDataBoundBeans(s, stepTester.configRoundTrip(s));
+        }
         // TODO uninstantiate works but SnippetizerTester.assertRoundTrip fails due to differing SCMSource.id values
         assertEquals("library identifier: 'foo@master', retriever: modernSCM([$class: 'GitSCMSource', credentialsId: '', remote: 'https://nowhere.net/', traits: [gitBranchDiscovery()]])", Snippetizer.object2Groovy(s));
         s.setRetriever(new SCMRetriever(new GitSCM(Collections.singletonList(new UserRemoteConfig("https://nowhere.net/", null, null, null)),