Update http2 syntax

roles/gitea/templates/nginx.conf.j2

@@ -37,10 +37,13 @@ server {
 {% if gitea_ssl_enabled is defined and
       gitea_ssl_enabled %}
 server {
-    listen 443 ssl http2;
+    listen 443 ssl;
 {% if ansible_all_ipv6_addresses | length %}
-    listen [::]:443 ssl http2;
+    listen [::]:443 ssl;
 {% endif %}
+
+    http2 on;
+
     server_name {{ gitea_domain }};
 
     access_log /var/log/nginx/gitea.access.log main;
@@ -62,6 +65,7 @@ server {
     }
 
     location / {
+        add_header Alt-Svc 'h3=":$server_port"; ma=86400';
         limit_req zone=req_bad_actors burst=10 nodelay;
         proxy_pass http://gitea_backend;
     }