Use latest available Apache Struts2 GA version 2.5.26

Author: jogep

aws-serverless-java-container-struts2/pom.xml

@@ -15,7 +15,7 @@
     </parent>
 
     <properties>
-        <struts2.version>2.5.22</struts2.version>
+        <struts2.version>2.5.26</struts2.version>
     </properties>
 
     <dependencies>