Upgrade nginx configuration following release 14 recommendations (https://docs.nextcloud.com/server/14/admin_manual/installation/nginx.html)

conf/nginx.conf

@@ -19,6 +19,7 @@ location ^~ __PATH__ {
   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;
 
   # Set max upload size
   client_max_body_size 10G;
@@ -85,6 +86,8 @@ location ^~ __PATH__ {
     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;
+
     # Optional: Don't log access to assets
     access_log off;
   }