Fix some formating. (extra '.', missing <code>)

Fix the number of available load balancer scheduler algorithms and add a link to the corresponding module. (lbmethod_heartbeat was missing in the list)

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1829613 13f79535-47bb-0310-9956-ffa450edef68