"listen ... http2" directive is deprecated

Using to `nginx 1.25.1` to check the config the following warnings are thrown:

```
/etc/nginx/conf.d # nginx -t
2023/08/04 13:53:03 [warn] 69#69: the "listen ... http2" directive is deprecated, use the "http2" directive instead in /etc/nginx/conf.d/listen_ssl.active:1
nginx: [warn] the "listen ... http2" directive is deprecated, use the "http2" directive instead in /etc/nginx/conf.d/listen_ssl.active:1
2023/08/04 13:53:03 [warn] 69#69: the "listen ... http2" directive is deprecated, use the "http2" directive instead in /etc/nginx/conf.d/listen_ssl.active:2
nginx: [warn] the "listen ... http2" directive is deprecated, use the "http2" directive instead in /etc/nginx/conf.d/listen_ssl.active:2
```

This fix results in the following output, fixing the issue:
```
/etc/nginx/conf.d # nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
```

data/conf/nginx/templates/listen_ssl.template

@@ -1,2 +1,3 @@
-listen ${HTTPS_PORT} ssl http2;
+listen ${HTTPS_PORT} ssl;
-listen [::]:${HTTPS_PORT} ssl http2;
+listen [::]:${HTTPS_PORT} ssl;
+http2 on;