fix documentatation, use _ instead of -
Merge branch 'systemd/multi-shell-support' into refs/top-bases/systemd/marc

* systemd/multi-shell-support:
  fix documentatation, use _ instead of -
Merge commit 'refs/top-bases/systemd/marc' into systemd/marc

* commit 'refs/top-bases/systemd/marc':
  fix documentatation, use _ instead of -