Fixes mongodb plugin params docs to be consistent
Fixes mongodb plugin params docs to be consistent

Rest of the document uses bullets rather than headings
archii/puppet-collectd,voxpupuli/puppet-collectd,juniorsysadmin/puppet-collectd,archii/puppet-collectd,voxpupuli/puppet-collectd,voxpupuli/puppet-collectd,archii/puppet-collectd,juniorsysadmin/puppet-collectd