sitePluginVersion property is used in ITs

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1507798 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 3e0e6b3..8ffc5a5 100644
--- a/pom.xml
+++ b/pom.xml
@@ -139,6 +139,7 @@
     <doxiaVersion>1.1.4</doxiaVersion>
     <mavenVersion>2.2.1</mavenVersion>
     <mavenPluginVersion>3.2</mavenPluginVersion>
+    <sitePluginVersion>3.3</sitePluginVersion><!-- used in ITs -->
   </properties>
 
   <dependencies>