fix: use `stdout` instead of `/dev/stdout`

`/dev/stdout` appears to have permissions issues, while the comments on this stackoverflow post[1] appear to indicate that stdout should work fine.

[1] https://stackoverflow.com/a/23328458/1515875

conf/app-nginx.conf.sigil

@@ -11,7 +11,7 @@ http {
   types_hash_max_size 2048;
   include mime.types;
   charset UTF-8;
-	access_log /dev/stdout;
+  access_log stdout;
   server {
     listen {{ $.PORT }};
     server_name  _;