installing from PPA does not work on Debian

This issue is about the [Linux install instructions](https://docs.qameta.io/allure/#_installing_a_commandline).

Aren't PPA an Ubuntu thing?

I'm surprised that the first command does something at all, though noisily:

```
# apt-add-repository ppa:qameta/allure

More info: https://launchpad.net/~qameta/+archive/ubuntu/allure
Press [ENTER] to continue or ctrl-c to cancel adding it

gpg: keybox '/tmp/tmprmlnijdh/pubring.gpg' created
gpg: /tmp/tmprmlnijdh/trustdb.gpg: trustdb created
gpg: key 35AEAEA4134BF6F3: public key "Launchpad PPA for Qameta Software" imported
gpg: Total number processed: 1
gpg: imported: 1
Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)).
gpg: no valid OpenPGP data found.
Exception in thread Thread-1:
Traceback (most recent call last):
File "/usr/lib/python3.9/threading.py", line 954, in _bootstrap_inner
self.run()
File "/usr/lib/python3.9/threading.py", line 892, in run
self._target(*self._args, **self._kwargs)
File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 688, in addkey_func
func(**kwargs)
File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 386, in add_key
return apsk.add_ppa_signing_key()
File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 273, in add_ppa_signing_key
cleanup(tmp_keyring_dir)
File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 234, in cleanup
shutil.rmtree(tmp_keyring_dir)
File "/usr/lib/python3.9/shutil.py", line 718, in rmtree
_rmtree_safe_fd(fd, path, onerror)
File "/usr/lib/python3.9/shutil.py", line 675, in _rmtree_safe_fd
onerror(os.unlink, fullname, sys.exc_info())
File "/usr/lib/python3.9/shutil.py", line 673, in _rmtree_safe_fd
os.unlink(entry.name, dir_fd=topfd)
FileNotFoundError: [Errno 2] No such file or directory: 'S.gpg-agent.extra'
```
The next command fails:
```
# apt-get update
Ign:1 http://ppa.launchpad.net/qameta/allure/ubuntu lunar InRelease
Hit:2 http://security.debian.org/debian-security bullseye-security InRelease
Hit:3 http://deb.debian.org/debian bullseye InRelease
Hit:4 https://fasttrack.debian.net/debian-fasttrack bullseye-fasttrack InRelease
Hit:5 http://deb.debian.org/debian bullseye-updates InRelease
Err:6 http://ppa.launchpad.net/qameta/allure/ubuntu lunar Release
404 Not Found [IP: 185.125.190.52 80]
Hit:7 https://updates.signal.org/desktop/apt xenial InRelease
Hit:8 https://fasttrack.debian.net/debian-fasttrack bullseye-backports-staging InRelease
Hit:9 https://baltocdn.com/helm/stable/debian all InRelease
Hit:10 https://apt.releases.hashicorp.com bullseye InRelease
Hit:11 https://packages.cloud.google.com/apt kubernetes-xenial InRelease
Hit:12 https://repo.platform.here.com/artifactory/debian stable InRelease
Reading package lists... Done
E: The repository 'http://ppa.launchpad.net/qameta/allure/ubuntu lunar Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
```

Perhaps the documentation should be changed to indicate that the PPA is for Ubuntu, not Debian?

Open the Linux install instructions at the linked Allure documentation page and review the PPA command in the installation section. Update the wording so readers can tell that the PPA is for Ubuntu rather than Debian, then verify that the resulting instructions accurately reflect the reported apt behavior.

Written by the indexing model from the issue text.