unbound/forwarders.conf.erb: add puppet warning
unbound/forwarders.conf.erb: add puppet warning

SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-profile