No Referrer-Policy header in nginx configuration example

[fa-ribeiro]

Nextcloud 14 checks in the setupchecks if the Referrer-Policy header is set (See: nextcloud/server#9122).
However, there is no reference to it in the nginx configuration example (https://github.com/nextcloud/documentation/blob/master/admin_manual/installation/nginx.rst).

[familyman-131]

here's options for nginx virtualhost

add_header X-Content-Type-Options nosniff;
add_header X-XSS-Protection "1; mode=block";
add_header X-Robots-Tag none;
add_header X-Download-Options noopen;
add_header X-Permitted-Cross-Domain-Policies none;
add_header Referrer-Policy no-referrer;
# Remove X-Powered-By, which is an information leak
fastcgi_hide_header X-Powered-By;

[J0WI]

Fixed in #856