Update downloads.xml

OR
https://web.archive.org/web/20171114155442/http://sixlegs.com/misc/ExcludeDoclet.java
diff --git a/downloads.xml b/downloads.xml
index d521011..65e965a 100644
--- a/downloads.xml
+++ b/downloads.xml
@@ -440,7 +440,7 @@
     </target>
     
     <target name="download-doclet-java" unless="doclet.zip.exists">
-        <get src="http://sixlegs.com/misc/ExcludeDoclet.java" 
+        <get src="https://github.com/couchbase/couchbase-lite-java-core/blob/master/extra/doclet/ExcludeDoclet.java" 
             dest="${modules.core.dir}/src/ExcludeDoclet.java" 
             verbose="false"/>
     </target>