prettify.js: update the js with the new Directives

Replaced the old list with what currently found in
https://httpd.apache.org/docs/current/mod/directives.html

This should allow a better highlight of new directives
like the mod_http2's ones



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1808454 13f79535-47bb-0310-9956-ffa450edef68