JCR-5000: update Apache parent pom to version 31

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/trunk@1913810 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/jackrabbit-parent/pom.xml b/jackrabbit-parent/pom.xml
index bcb2729..0a0841b 100644
--- a/jackrabbit-parent/pom.xml
+++ b/jackrabbit-parent/pom.xml
@@ -27,7 +27,7 @@
   <parent>
     <groupId>org.apache</groupId>
     <artifactId>apache</artifactId>
-    <version>30</version>
+    <version>31</version>
     <relativePath />
   </parent>