Add nicer error for Pro commands such as `up deploys` in the OSS version

## Prerequisites

* [x] I am running the latest version. (`up upgrade`)
* [x] I searched to see if the issue already exists.
* [x] I inspected the verbose debug output with the `-v, --verbose` flag.
* [ ] Are you an Up Pro subscriber?

```bash
$ up deploys
Error: "deploys" is invalid, must be one of:

• production
• staging
```
Then I tried
```bash
$ up deploys staging
Error: unexpected staging
```

According to the docs, this should work. Am I missing something really obvious?