Logstash xpack monitoring wrong config

[hriegger (Harry RIegger)]

In file /usr/share/logstash/x-pack/lib/template.cfg.erb document_type is defined, where elasticsearch > 7.0 doesn't support this.

@hriegger

output {
elasticsearch {
hosts => <%= es_hosts %>
bulk_path => "/_monitoring/bulk?system_id=logstash&system_api_version=<%= system_api_version %>&interval=1s"
manage_template => false
document_type => "%{[@metadata][document_type]}"
index => ""