##### SUMMARY
With the introduction of `Collection` mechanism using the `ansible-galaxy` CLI, the command and sub command help texts should be reflecting the new feature. The CLI currently validates the `collection` sub-command but the help text is still saying `role` is the only valid sub-command.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
`ansible-galaxy`

##### ANSIBLE VERSION
```
ansible 2.9.7
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/home/dvercill/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/dvercill/.local/lib/python3.8/site-packages/ansible
  executable location = /home/dvercill/.local/bin/ansible
  python version = 3.8.2 (default, Feb 28 2020, 00:00:00) [GCC 10.0.1 20200216 (Red Hat 10.0.1-0.8)]
```

##### CONFIGURATION
N/A

##### OS / ENVIRONMENT
Fedora Workstation 32 beta

##### STEPS TO REPRODUCE
```
$ ansible-galaxy doesnotexist
usage: ansible-galaxy role [-h] ROLE_ACTION ...
ansible-galaxy role: error: argument ROLE_ACTION: invalid choice: 'doesnotexist' (choose from 'init', 'remove', 'delete', 'list', 'search', 'import', 'setup', 'login', 'info', 'install')
```
options = context.CLIARGS
        
        loader = DataLoader()
        basedir = options.get('basedir', False)
        if basedir:
            loader.set_basedir(basedir)
            add_all_plugin_dirs(basedir)
            AnsibleCollectionConfig.playbook_paths = basedir
            default_collection = _get_collection_name_from_path(basedir)
            if default_collection:
                display.warning(u'running with default collection {0}'.format(default_collection))
                AnsibleCollectionConfig.default_collection = default_collection
        vault_ids = list(options['vault_ids'])
        default_vault_ids = C.DEFAULT_VAULT_IDENTITY_LIST
        vault_ids = default_vault_ids + vault_ids
        vault_secrets = CLI.setup_vault_secrets(loader,
                                                vault_ids=vault_ids,
                                                vault_password_files=list(options['vault_password_files']),
                                                ask_vault_pass=options['ask_vault_pass'],
                                                auto_prompt=False)
        loader.set_vault_secrets(vault_secrets)
        
        inventory = InventoryManager(loader=loader, sources=options['inventory'])
        
        
        variable_manager = VariableManager(loader=loader, inventory=inventory, version_info=CLI.version_info(gitinfo=False))
        return loader, inventory, variable_manager
    @staticmethod
    def get_host_list(inventory, subset, pattern='all'):