Revert introduction of H2PushResource on 2.4 docs

The directive will be available only from 2.4.24 onwards,
reverting to avoid confusing users.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1769791 13f79535-47bb-0310-9956-ffa450edef68