Fix alias paths in nginx config

[tutasla]

This is a best practice change for nginx config. There is no misconfiguration at the moment.

There are two reasons for making these changes:

1. It is recommended by the official docs.
2. Prevents path traversal bugs that might happen due to future changes in configs:

// not vulnerable to path traversal (current)
 location /static {
      alias /usr/share/nginx/html/static;

// vulnerable to path traversal (example)
 location /static {
      alias /usr/share/nginx/html/static/;

Docs & References:
https://nginx.org/en/docs/http/ngx_http_core_module.html#alias
https://github.com/yandex/gixy/blob/master/docs/en/plugins/aliastraversal.md
https://blog.detectify.com/2020/11/10/common-nginx-misconfigurations/

[Maffooch]

Good fix. Thanks!