### Summary

Our setuptools constrain in `pyproject.toml` (listed also in `setup.cfg`) is set to `>= 39.2.0` due to the minimum version available at the time on Ubuntu 18.04.

Now that we have a dependency on Python 3.9 as a minimum, that constraint no longer makes sense, as Python 3.9 is not available on 18.04, and the `dist-packages` `setuptools==39.2.0` compat between deadsnakes python3.9 is non-functional.

This would make Ubuntu 20.04 effectively the minimum supported controller.  The `dist-packages` `setuptools==45.2.0` is functional with the `python3.9` package, and works fine with our packaging.  

This doesn't really grant us anything, since we're waiting for the minimum to eventually be `51.0.0` so we can list the `entry_points` in `pyproject.toml`, but no need to list effectively a non-functional lower bounds. 

### Issue Type

Feature Idea

### Component Name

pyproject.toml

### Additional Information

<!--- Paste example playbooks or commands between quotes below -->
```yaml (paste below)

```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
for filename in _find_symlinks():
        if filename not in complete_file_list:
            
            
            complete_file_list.append(filename)
    
    with clean_repository(complete_file_list) as clean_repo_dir:
        os.chdir(clean_repo_dir)
        to_ship_files = assemble_files_to_ship(complete_file_list)
        to_install_files = assemble_files_to_install(complete_file_list)
        results = []
        with tempfile.TemporaryDirectory() as tmp_dir:
            sdist_path = create_sdist(tmp_dir)
            sdist_dir = extract_sdist(sdist_path, tmp_dir)
            
            results.extend(check_sdist_contains_expected(sdist_dir, to_ship_files))
            
            results.extend(check_sdist_files_are_wanted(sdist_dir, to_ship_files))
            
            install_dir = install_sdist(tmp_dir, sdist_dir)
            
            results.extend(check_installed_contains_expected(install_dir, to_install_files))
            
            results.extend(check_installed_files_are_wanted(install_dir, to_install_files))
        for message in results:
            print(message)
if __name__ == '__main__':
    main()