Add latest JDK in Travis

Signed-off-by: Jorge Bescos Gascon <jorge.bescos.gascon@oracle.com>

.travis.yml

@@ -1,10 +1,21 @@
+# Copyright (c) 2021 Oracle and/or its affiliates. All rights reserved.
+#
+# This program and the accompanying materials are made available under the
+# terms of the Eclipse Public License v. 2.0 which is available at
+# http://www.eclipse.org/legal/epl-2.0,
+# or the Eclipse Distribution License v. 1.0 which is available at
+# http://www.eclipse.org/org/documents/edl-v10.php.
+#
+# SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
+#
+
 dist: bionic
 
 language: java
 
 jdk:
   - openjdk11
-  - openjdk15
+  - openjdk-ea
 
 cache:
   directories: