nginx: Moved index directive from root snippet to specific static role

roles/nginx/application/templates/root.conf

@@ -1,3 +1 @@
 include {{ nginx_snippets_directory }}/global;
-
-index index.html index.htm;

roles/nginx/static/templates/static.conf

@@ -7,6 +7,7 @@ server {
   ssl_certificate {{ acme_certificate_location }};
   ssl_certificate_key {{ acme_key_location }};
 
+  index index.html index.htm;
   root {{ root_directory }};
 
   include {{ nginx_snippets_directory }}/https;