modules: ffmuc-mesh-vpn-wireguard: Cleanup Code

[grische]

See https://github.com/freifunk-gluon/community-packages/pull/107

[github-actions[bot]]

Backport failed for legacy, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin legacy
git worktree add -d .worktree/backport-419-to-legacy origin/legacy
cd .worktree/backport-419-to-legacy
git switch --create backport-419-to-legacy
git cherry-pick -x 721c66901cf786c52d5f64df5b7c2b41a5ebc49b

• 425

[github-actions[bot]]

Successfully created backport PR for next:

• 421