### Summary

The `apt_repository` will fail with a somewhat confusing error if gnugp, and dirmngr manager are not installed.  Neither of these packages are Required/Essential/Important, and may not be already installed in minimal systems that you might want to run `apt_repository` on.

The fix might be to just include `gnupg` in the requirements section of the docs.

### Issue Type

Documentation Report

### Component Name

apt_repository

### Ansible Version

```console
$  ansible --version
ansible [core 2.11.4]
  config file = ...
  configured module search path = ...
  ansible python module location = ...
  ansible collection location = ...
  executable location = /usr/local/bin/ansible
  python version = 3.9.2 (default, Feb 28 2021, 17:03:44) [GCC 10.2.1 20210110]
  jinja version = 3.0.1
  libyaml = True
```


### Configuration

```console
$ ansible-config dump --only-changed
```


### OS / Environment

Mostly a docs issue so this is N/A. But apt_repository applies to Debian, Ubuntu, and forks.

### Additional Information

Tells people that need gnupg when using apt_repository.

### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
- Whether to automatically try to install the Python apt library or not, if it is not already installed.
              Without this library, the module does not work.
            - Runs C(apt-get install python-apt) for Python 2, and C(apt-get install python3-apt) for Python 3.
            - Only works with the system Python 2 or Python 3. If you are using a Python on the remote that is not
               the system Python, set I(install_python_apt=false) and ensure that the Python apt library
               for your Python version is installed some other way.
        type: bool
        default: true
author:
- Alexander Saltanov (@sashka)
version_added: "0.7"
requirements:
   - python-apt (python 2)
   - python3-apt (python 3)
'''
EXAMPLES = '''
- name: Add specified repository into sources list
  ansible.builtin.apt_repository:
    repo: deb http://archive.canonical.com/ubuntu hardy partner
    state: present
- name: Add specified repository into sources list using specified filename
  ansible.builtin.apt_repository:
    repo: deb http://dl.google.com/linux/chrome/deb/ stable main
    state: present
    filename: google-chrome
- name: Add source repository into sources list
  ansible.builtin.apt_repository:
    repo: deb-src http://archive.canonical.com/ubuntu hardy partner
    state: present
- name: Remove specified repository from sources list