feat: update http2 nginx directive

[74k1]

• fixes "Nginx Config improvement" Fix #529
• duplicate entries has already gotten a fix by remove duplication from proxy config #555

[micbar]

@Svanvith @ScharfViktor We need to test it before merging.

@74k1 Thanks for the PR!

[ScharfViktor]

I have nginx/1.24.0 on Ubuntu 24.04.3 LTS, and it is not working. Do I need to update the nginx version? And should I write in the documentation which version of nginx to use?

sudo nginx -t && sudo systemctl reload nginx
2026/01/07 09:52:03 [emerg] 1380651#1380651: unknown directive "http2" in /etc/nginx/sites-enabled/opencloud:19
nginx: configuration file /etc/nginx/nginx.conf test failed
root@test-release:/opt/opencloud-compose# nginx -v
nginx version: nginx/1.24.0 (Ubuntu)
root@test-release:/opt/opencloud-compose# lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 24.04.3 LTS
Release:	24.04
Codename:	noble

[ScharfViktor]

To maintain compatibility, I suggest leaving the old version of the documentation as the default and adding a new config for nginx 1.25 and higher.
cc @micbar