Posgres errors when running `coder` should suggest `--dev`

I forgot to add hypens before `dev`. 
```
$ coder start dev
Error: ping postgres: dial tcp [::1]:5432: connect: connection refused
```

It would be nice to suggest using `--dev`.

```
$ coder start dev
Error: ping postgres: dial tcp [::1]:5432: connect: connection refused

Tip: If you are trying to run coder without a persistent database, use `coder start --dev ...`
```