Per the example in https://github.com/octokit/core.js/#rest-api-example
the value for the `auth` property in the `Octokit` constructor is now just
the personal access token, not `token $TOKEN`. The old format still
works with a recently generated token though.

To test:

```sh
export GITHUB_TOKEN=$TOKEN
node scripts/generate-change-list.js $PREV_CLIENT_VERSION
```

Where `$TOKEN` is a token generated at https://github.com/settings/tokens and
`$PREV_CLIENT_VERSION` is the previous released version of the client to
use as a starting point for the change list.