set parent version to 24 and add empty relativePath where missing

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1689593 13f79535-47bb-0310-9956-ffa450edef68

pom.xml

diff --git a/pom.xml b/pom.xml
index c4439b8..729315a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -21,8 +21,8 @@
     <parent>
         <groupId>org.apache.sling</groupId>
         <artifactId>sling</artifactId>
-        <version>23</version>
-        <relativePath />
+        <version>24</version>
+        <relativePath/>
     </parent>
     <modelVersion>4.0.0</modelVersion>