Update deprecated http2 nginx conf syntax

[ctmbl]

Justified by:

± docker logs blogiscscfr-blog-1 | tail
2024/04/26 22:21:23 [warn] 8#8: the "listen ... http2" directive is deprecated, use the "http2" directive instead in /etc/nginx/nginx.conf
nginx: [warn] the "listen ... http2" directive is deprecated, use the "http2" directive instead in /etc/nginx/nginx.conf

Also:

• https://github.com/nginxinc/kubernetes-ingress/issues/4237
• https://www.nginx.com/blog/nginx-plus-r30-released/#Important-Changes-in-Behavior-