NIFIREG-366: updating pom parent version

Signed-off-by: Pierre Villard <pierre.villard.fr@gmail.com>

This closes #263.
diff --git a/pom.xml b/pom.xml
index 5e6108b..e9e26c8 100644
--- a/pom.xml
+++ b/pom.xml
@@ -19,7 +19,7 @@
     <parent>
         <groupId>org.apache</groupId>
         <artifactId>apache</artifactId>
-        <version>17</version>
+        <version>23</version>
         <relativePath />
     </parent>
     <groupId>org.apache.nifi.registry</groupId>