ansible: nginx: Don't send version number

The version number isn't really needed for anything,
and it makes us a more interesting target for automated vulnerability crawlers.

ansible/roles/nginx/files/nginx.conf

@@ -22,7 +22,7 @@ http {
 	sendfile on;
 	tcp_nopush on;
 	types_hash_max_size 2048;
-	# server_tokens off;
+	server_tokens off;
 
 	# server_names_hash_bucket_size 64;
 	# server_name_in_redirect off;