##### SUMMARY
The PR https://github.com/ansible/ansible/pull/64156 deprecated passing extra variables on `import_playbook`, which was wrongly stated to have never worked before, but it does, as shown in the example below.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
- `import_playbook`

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.10.3
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/home/goetz/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python3.8/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 3.8.6 (default, Sep 30 2020, 04:00:38) [GCC 10.2.0]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below
[no output]
```

##### OS / ENVIRONMENT
- GNU/Linux

##### STEPS TO REPRODUCE
`playbooks/site.yaml`:
```yaml
---
- hosts: "{{ target }}"
  roles:
    - role: my-role
```

`playbooks/dev.yaml`:
```yaml
---
- import_playbook: site.yml target='dev'
```

```sh
ansible-playbook playbooks/dev.yml
```

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
Playbook runs without warnings or errors.

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->
Playbooks shows a Warning about this behavior going to fail in a future Ansible minor version update.
```sh
[WARNING]: Additional parameters in import_playbook statements are not supported. This will be an error in version 2.14
```


self.collection_version = None
        self.collection_name = None
        super(AnsibleDeprecatedChecker, self).__init__(*args, **kwargs)
    def set_option(self, optname, value, action=None, optdict=None):
        super(AnsibleDeprecatedChecker, self).set_option(optname, value, action, optdict)
        if optname == 'collection-version' and value is not None:
            self.collection_version = SemanticVersion(self.config.collection_version)
        if optname == 'collection-name' and value is not None:
            self.collection_name = self.config.collection_name
    def _check_date(self, node, date):
        if not isinstance(date, str):
            self.add_message('invalid-date', node=node, args=(date,))
            return
        try:
            date_parsed = parse_isodate(date)
        except ValueError:
            self.add_message('ansible-invalid-deprecated-date', node=node, args=(date,))
            return
        if date_parsed < datetime.date.today():
            self.add_message('ansible-deprecated-date', node=node, args=(date,))
    def _check_version(self, node, version, collection_name):