[stable27] docs(admin): revise the brute force protection configuration chapter

[backportbot[bot]]

Backport of #11541

Warning, This backport's changes differ from the original and might be incomplete ⚠️

Todo

• [ ] Review and resolve any conflicts
• [ ] Amend HEAD commit to remove [skip ci] tag

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[nickvergessen]

Due to the issues I would simply not backport it.