Fix incorrect server_name for Jitsi

Fixes #417 (Github Issue)

roles/matrix-nginx-proxy/templates/nginx/conf.d/matrix-jitsi.conf.j2

@@ -56,7 +56,7 @@ server {
 	listen {{ 8443 if matrix_nginx_proxy_enabled else 443 }} ssl http2;
 	listen [::]:{{ 8443 if matrix_nginx_proxy_enabled else 443 }} ssl http2;
 
-	server_name {{ matrix_nginx_proxy_proxy_dimension_hostname }};
+	server_name {{ matrix_nginx_proxy_proxy_jitsi_hostname }};
 
 	server_tokens off;
 	root /dev/null;