only accept forgejo logs for now

ansible/roles/monitoring/fluent.conf.j2

@@ -6,7 +6,7 @@
   port {{ fluent_forward_port }}
 </source>
 
-<match **>
+<match cpu memory diskfree docker.forgejo_forgejo.**>
   @type elasticsearch
   host maestro.dmz
   port {{ elasticsearch_port }}
@@ -15,6 +15,10 @@
   logstash_prefix fluentd.${tag}
 </match>
 
+<match **>
+  @type null
+</match>
+
 <system>
   log_level info
 </system>