ZOOKEEPER-2465: Documentation copyright notice is out of date.

Author: Edward Ribeiro <edward.ribeiro@gmail.com>

Reviewers: Michael Han <hanm@apache.org>

Closes #138 from eribeiro/ZOOKEEPER-2465

(cherry picked from commit 5c9299d60f66afb00072ebeadead49f4410aa11f)
Signed-off-by: Michael Han <hanm@apache.org>

src/docs/src/documentation/skinconf.xml

@@ -84,7 +84,7 @@ which will be used to configure the chosen Forrest skin.
   <favicon-url>images/favicon.ico</favicon-url>
 
   <!-- The following are used to construct a copyright statement -->
-  <year>2008-2013</year>
+  <year></year>
   <vendor>The Apache Software Foundation.</vendor>
   <copyright-link>http://www.apache.org/licenses/</copyright-link>