[SHIRO-882] Upgrade to apache pom parent 26

Cherry-picked from: #356

Author: fpapon

pom.xml

@@ -24,7 +24,7 @@
     <parent>
         <groupId>org.apache</groupId>
         <artifactId>apache</artifactId>
-        <version>25</version>
+        <version>26</version>
     </parent>
 
     <groupId>org.apache.shiro</groupId>