Use @code instead of <code>

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1471359 13f79535-47bb-0310-9956-ffa450edef68
fix Javadoc

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1471360 13f79535-47bb-0310-9956-ffa450edef68