fixing typo in untaint help file

[AHaymond]

This is a 🧐 documentation change.

• [ x ] I've added tests (if it's a bug, feature or enhancement)
• [ x ] I've adjusted the documentation (if it's a feature or enhancement)
• [ x ] The test suite passes (run bundle exec rspec to verify this)

Summary

This is merely a documentation typo fix.

Context

A help file is utilizing the wrong command in its example input, and was originally my mistake.

How to Test

No testing necessary