### Summary

While specifying requirements.yml to install roles like - 

```
ansible-galaxy role install -r requirements.yml -vvvv
```

With `requirements.yml` (I understand this file syntax is wrong)

```yaml
---
community.vmware
```

results in 
```
ERROR! Unexpected Exception, this is probably a bug: 'str' object has no attribute 'keys'
the full traceback was:

Traceback (most recent call last):
  File "/Volumes/data/src/ansible/lib/ansible/cli/__init__.py", line 659, in cli_executor
    exit_code = cli.run()
                ^^^^^^^^^
  File "/Volumes/data/src/ansible/bin/ansible-galaxy", line 749, in run
    return context.CLIARGS['func']()
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Volumes/data/src/ansible/bin/ansible-galaxy", line 120, in method_wrapper
    return wrapped_method(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Volumes/data/src/ansible/bin/ansible-galaxy", line 1368, in execute_install
    requirements = self._parse_requirements_file(
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Volumes/data/src/ansible/bin/ansible-galaxy", line 840, in _parse_requirements_file
    extra_keys = set(file_requirements.keys()).difference(set(['roles', 'collections']))
                     ^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'str' object has no attribute 'keys'
```

### Issue Type

Bug Report

### Component Name

ansible-galaxy

### Ansible Version

```console
$ ansible --version
ansible [core 2.17.0.dev0] (i81713 310625996d) last updated 2023/10/04 11:27:33 (GMT -400)
  config file = /Volumes/data/src/playbooks/ansible.cfg
  configured module search path = ['/Users/akasurde/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Volumes/data/src/ansible/lib/ansible
  ansible collection location = /Users/akasurde/.ansible/collections:/usr/share/ansible/collections
  executable location = /Volumes/data/src/ansible/bin/ansible
  python version = 3.11.3 (main, May 10 2023, 12:50:08) [Clang 14.0.3 (clang-1403.0.22.14.1)] (/Users/akasurde/.pyenv/versions/3.11.3/bin/python)
  jinja version = 3.1.2
  libyaml = True
```


### Configuration

```console
# if using a version older than ansible-core 2.12 you should omit the '-t all'
$ ansible-config dump --only-changed -t all
```


### OS / Environment

Red Hat Enterprise Linux release 8.2 (Ootpa)

### Steps to Reproduce

Trying installing role/collection with the above requirements.yml file.


### Expected Results

Installation successful.

### Actual Results

```console
ERROR! Unexpected Exception, this is probably a bug: 'str' object has no attribute 'keys'
the full traceback was:

Traceback (most recent call last):
  File "/Volumes/data/src/ansible/lib/ansible/cli/__init__.py", line 659, in cli_executor
    exit_code = cli.run()
                ^^^^^^^^^
  File "/Volumes/data/src/ansible/bin/ansible-galaxy", line 749, in run
    return context.CLIARGS['func']()
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Volumes/data/src/ansible/bin/ansible-galaxy", line 120, in method_wrapper
    return wrapped_method(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Volumes/data/src/ansible/bin/ansible-galaxy", line 1368, in execute_install
    requirements = self._parse_requirements_file(
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Volumes/data/src/ansible/bin/ansible-galaxy", line 840, in _parse_requirements_file
    extra_keys = set(file_requirements.keys()).difference(set(['roles', 'collections']))
                     ^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'str' object has no attribute 'keys'
```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
test_path = collll[2]
    expected = 'You must specify a collection name or a requirements file.'
    with pytest.raises(AnsibleError, match=expected):
        GalaxyCLI(args=['ansible-galaxy', 'collection', 'install', '--collections-path', test_path]).run()
def test_collll_path_with_ansible_collections(collll):
    mock_install, mock_warning, output_dir = collll
    collection_path = os.path.join(output_dir, 'ansible_collections')
    galaxy_args = ['ansible-galaxy', 'collection', 'install', 'namespace.collection', 'namespace2.collection:1.0.1',
                   '--collections-path', collection_path]
    GalaxyCLI(args=galaxy_args).run()
    rt os.path.isdir(collection_path)
    rt mock_warning.call_count == 1
    rt "The specified collections path '%s' is not part of the configured Ansible collections path" \
        % collection_path in mock_warning.call_args[0][0]
    rt ml_count == 1
    requirements = [('%s.%s' % (r.namespace, r.name), r.ver, r.src, r.type,) for r in ml_args[0][0]]
    rt requirements == [('namespace.collection', '*', None, 'galaxy'),
                            ('namespace2.collection', '1.0.1', None, 'galaxy')]
    rt ml_args[0][1] == collection_path
    rt len(ml_args[0][2]) == 1
    rt ml_args[0][2][0].api_server == 'https://galaxy.ansible.com'
    rt ml_args[0][2][0].validate_certs is True
    rt ml_args[0][3] is False  # ignore_errors
    rt ml_args[0][4] is False  # no_deps
    rt ml_args[0][5] is False  # force
    rt ml_args[0][6] is False  # force_deps
def test_collll_ignore_certs(collll):