Link broken in README

[paulz1]

In the README, in the part "HTTPS web interface" the link to default.conf is broken.

Actually it's
https://github.com/monitoringartist/dockbix-xxl/blob/master/Dockerfile/dockbix-xxl/container-files-zabbix/etc/nginx/hosts.d/default.conf
but this URL does not exist.

Probably it's should be
https://github.com/monitoringartist/dockbix-xxl/blob/master/Dockerfile/dockbix-xxl-4.0/container-files-zabbix/etc/nginx/hosts.d/default.conf
(using dockbix-xxl-4.0 instead of dockbix-xxl).

Sure, it's not very important. But in the same time it's vrey confusing when we click on link and get Git 404 page.