### 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
new_vault_ids = []
            if encrypt_vault_id:
                new_vault_ids = default_vault_ids
            if context.CLIARGS['new_vault_id']:
                new_vault_ids.append(context.CLIARGS['new_vault_id'])
            new_vault_password_files = []
            if context.CLIARGS['new_vault_password_file']:
                new_vault_password_files.append(context.CLIARGS['new_vault_password_file'])
            new_vault_secrets = \
                self.setup_vault_secrets(loader,
                                         vault_ids=new_vault_ids,
                                         vault_password_files=new_vault_password_files,
                                         ask_vault_pass=context.CLIARGS['ask_vault_pass'],
                                         create_new_password=True)
            if not new_vault_secrets:
                raise AnsibleOptionsError("A new vault password is required to use Ansible's Vault rekey")
            
            
            new_encrypt_secret = match_encrypt_secret(new_vault_secrets,
                                                      encrypt_vault_id=encrypt_vault_id)
            self.new_encrypt_vault_id = new_encrypt_secret[0]
            self.new_encrypt_secret = new_encrypt_secret[1]
        loader.set_vault_secrets(vault_secrets)
        
        vault = VaultLib(vault_secrets)
        self.editor = VaultEditor(vault)
        context.CLIARGS['func']()
        
        os.umask(old_umask)
    def execute_encrypt(self):