Update release schedule page

git-svn-id: https://svn.apache.org/repos/asf/karaf/site/trunk@1608163 13f79535-47bb-0310-9956-ffa450edef68
Update release schedule page

git-svn-id: https://svn.apache.org/repos/asf/karaf/site/trunk@1608164 13f79535-47bb-0310-9956-ffa450edef68