Update to expect maven 3 when creating the site.

git-svn-id: https://svn.apache.org/repos/asf/webservices/commons/trunk/modules/XmlSchema@1026689 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 89b6f1f..73c9e11 100644
--- a/pom.xml
+++ b/pom.xml
@@ -238,7 +238,9 @@
                     </configuration>
                 </plugin>
                 <plugin>
+		    <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-site-plugin</artifactId>
+		    <version>3.0-beta-2</version>
                     <executions>
                         <execution>
                             <id>site</id>