### Summary

`ansible-vault encrypt_string --help` shows the `--output` option but it remains without effect.

### Issue Type

Bug Report

### Component Name

ansible-vault

### Ansible Version

```console
$ ansible --version
ansible 2.9.21
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/home/elavarde/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python3.9/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 3.9.5 (default, May 14 2021, 00:00:00) [GCC 11.1.1 20210428 (Red Hat 11.1.1-1)]
```


### Configuration

```console
$ ansible-config dump --only-changed
[... empty ...]
```


### OS / Environment

Fedora 34

### Steps to Reproduce

```shell
ansible-vault encrypt_string --ask-vault-pass --name myvar --output vault.yml 'some secret'
```


### Expected Results

Variable and its encrypted content are written to file and not to stdout _or_ the option `--output` isn't shown in the help.

Making the `--output` version working would probably be a duplicate of issue #59590, so probably removing the `--output` option which doesn't work could be a simpler step. More important for now is that it's consistent.

### Actual Results

```console
- output file isn't created/edited
- variable and its content are output to stdout
```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
show_delimiter = False
        if len(b_plaintext_list) > 1:
            show_delimiter = True
        
        output = []
        
        
        
        for index, b_plaintext_info in enumerate(b_plaintext_list):
            
            b_plaintext, src, name = b_plaintext_info
            b_ciphertext = self.editor.encrypt_bytes(b_plaintext, self.encrypt_secret,
                                                     vault_id=vault_id)
            
            yaml_text = self.format_ciphertext_yaml(b_ciphertext, name=name)
            err_msg = None
            if show_delimiter:
                human_index = index + 1
                if name:
                    err_msg = '# The encrypted version of variable ("%s", the string #%d from %s).\n' % (name, human_index, src)
                else:
                    err_msg = '# The encrypted version of the string #%d from %s.)\n' % (human_index, src)
            output.append({'out': yaml_text, 'err': err_msg})
        return output
    def execute_decrypt(self):