Example in README.md is outdated

## Description
The following example in the README.md file is outdated

## Actual wording
```
You can then perform calls to the API on behalf of an Organization:

projects, err := org.ListProjects(ctx)
```

## Expected wording
```
You can then perform calls to the API on behalf of an Organization:

projects, response, err := org.ListProjects(ctx)
```
