Outdated instructions for HTTPS/WSS in the wiki

[rnestler]

In the wiki under https://github.com/jaedb/Iris/wiki/Advanced#encryption-httpswss there are example configurations for nginx. These are outdated and need to be changed:

• Remove ssl directive (outdated since 1.15.0 and removed in 1.25.1, see https://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl)
• I'm not sure why / is redirected to /iris
• I needed to change the proxy_set_header directives for it to work:

              proxy_set_header Upgrade $http_upgrade;
              proxy_set_header Connection "upgrade";
              proxy_set_header Host $http_host;