docs: update the compliance-trestle-fedramp plugin usage

[jpower432]

Types of changes

• [ ] Hot fix (emergency fix and release)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [X] Documentation (change which affects the documentation site)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Release (develop -> main)

Quality assurance (all should be covered).

• [X] My code follows the code style of this project.
• [X] Documentation for my change is up to date?
• [ ] My PR meets testing requirements.
• [X] All new and existing tests passed.
• [X] All commits are signed-off.

Summary

Documentation updates for the compliance-trestle-fedramp plugin. Relates to this PR.

Key links:

• Sonar coverage

Before you merge

• Ensure it is a 'squash commit' if not a release.
• Ensure CI is currently passing
• Check sonar. If you are working for a fork a maintainer will reach out, if required.