Revert "increase timeout for the nginx proxy that provides access to the Mail…" (#2411)

Reverts #2407 - as per #2316

This reverts commit 2803d88894.

conf/nginx-primaryonly.conf

@@ -8,7 +8,6 @@
 	rewrite ^/admin/munin$ /admin/munin/ redirect;
 	location /admin/ {
 		proxy_pass http://127.0.0.1:10222/;
-		proxy_read_timeout 600s;
 		proxy_set_header X-Forwarded-For $remote_addr;
 		add_header X-Frame-Options "DENY";
 		add_header X-Content-Type-Options nosniff;