Contrib: remove superflous sling.java.version=6 as it's the default now

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1687508 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 58084be..e8e1d74 100644
--- a/pom.xml
+++ b/pom.xml
@@ -39,7 +39,6 @@
   </description>
 
   <properties>
-    <sling.java.version>6</sling.java.version>
     <pax.exam.version>3.4.0</pax.exam.version>
     <pax.url.version>1.6.0</pax.url.version>
     <bundle.build.name>