### 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
source = self._parse(line, raise_if_invalid_or_disabled=True)[2]
        
        self._add_valid_source(source, comment, file=file or self._suggest_filename(source))
    def _remove_valid_source(self, source):
        
        for filename, n, enabled, src, comment in self:
            if source == src and enabled:
                self.files[filename].pop(n)
    def remove_source(self, line):
        source = self._parse(line, raise_if_invalid_or_disabled=True)[2]
        self._remove_valid_source(source)
class UbuntuSourcesList(SourcesList):