nginx: remove combined2 custom log format

collectd does not use this anymore (eb47476c83)

This makes nginx work better with a variety of tools like Wazuh and ossec

https://forum.cloudron.io/topic/6077/nginx-logs-format/
https://forum.cloudron.io/topic/6161/implement-default-nginx-logging

setup/start/nginx/nginx.conf

@@ -19,15 +19,10 @@ http {
     include       mime.types;
     default_type  application/octet-stream;
 
-    # the collectd config depends on this log format
-    log_format combined2 '$remote_addr - [$time_local] '
-        '"$request" $status $body_bytes_sent $request_time '
-        '"$http_referer" "$host" "$http_user_agent"';
-
     # required for long host names
     server_names_hash_bucket_size 128;
 
-    access_log /var/log/nginx/access.log combined2;
+    access_log /var/log/nginx/access.log combined;
 
     sendfile        on;