Correct default rails environment

Whoops, that's my mistake, unless the default has been changed recently.

Do we want the default to be development? I guess that makes sense, because is someone is setting up a production pod they really ought to be going through the settings to make sure they're correct.

As well as removing 'Only', you can remove 'or test', I'd imagine, so the line reads 'Change this if you wish to run a production environment'.