Improve promote-to-primary-node command

What does this MR do?

Improve promote-to-primary-node command by

• removing unused option confirm-removing-keys,
• improving description for skip-preflight-checks (gitlab#225534 (comment 376646244))

Closes gitlab#227566 (closed)

Related issues

Checklist

See Definition of done.

• Changelog entry created. Not applicable for Documentation changes and minor changes.
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA, if applicable
• MR targeting master branch
• MR has a green pipeline on GitLab.com
• Equivalent MR/issue for CNG opened if applicable
• trigger-package has a green pipeline running against latest commit

Reviewer Checklist

In addition to above, reviewer must:

• Pipeline is green on dev.gitlab.org if the change is not touching documentation or internal cookbooks