set parent version to 24 and add empty relativePath where missing

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1689588 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 73c3414..8ff0ab0 100644
--- a/pom.xml
+++ b/pom.xml
@@ -24,7 +24,7 @@
   <parent>
     <groupId>org.apache.sling</groupId>
     <artifactId>sling</artifactId>
-    <version>23</version>
+    <version>24</version>
     <relativePath/>
   </parent>