feat(repo): use a PPA for the latest version of nextcloud-desktop

[alxwr]

PR progress checklist (to be filled in by reviewers)

• Changes to documentation are appropriate (or tick if not required)
• Changes to tests are appropriate (or tick if not required)
• Reviews completed

---

What type of PR is this?

Primary type

• [build] Changes related to the build system
• [chore] Changes to the build process or auxiliary tools and libraries such as documentation generation
• [ci] Changes to the continuous integration configuration
• [feat] A new feature
• [fix] A bug fix
• [perf] A code change that improves performance
• [refactor] A code change that neither fixes a bug nor adds a feature
• [revert] A change used to revert a previous commit
• [style] Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc.)

Secondary type

• [docs] Documentation changes
• [test] Adding missing or correcting existing tests

Does this PR introduce a BREAKING CHANGE?

No.

Related issues and/or pull requests

none

Describe the changes you're proposing

Use a PPA for Ubuntu, with an opt-out via Pillar.

Pillar / config required to test the proposed changes

nextcloud:
  use_ppa: True

Debug log showing how the proposed changes work

myhost;
----------
          ID: nextcloud--client--repo--ppa
    Function: pkgrepo.managed
      Result: True
     Comment: Configured package repo 'nextcloud--client--repo--ppa'
     Started: 22:15:56.366124
    Duration: 15037.52 ms
     Changes:   
              ----------
              repo:
                  ppa:nextcloud-devs/client
----------
          ID: nextcloud-client-install-pkg-installed
    Function: pkg.installed
      Result: True
     Comment: All specified packages are already installed
     Started: 22:16:12.335312
    Duration: 148.116 ms
     Changes:   

Summary for myhost
------------
Succeeded: 2 (changed=1)
Failed:    0
------------
Total states run:     2
Total run time:  15.186 s

Documentation checklist

• Updated the README (e.g. Available states).
• Updated pillar.example.

Testing checklist

• Included in Kitchen (i.e. under state_top).
• Covered by new/existing tests (e.g. InSpec, Serverspec, etc.).
• Updated the relevant test pillar.

Additional context