Update outdated links in Markdown files tripping link checker

[aj-stein-nist]

Committer Notes

Update FedRAMP GH links to updated paths, fixes #1523.

See last nightly link checker run for more details via URL below.

https://github.com/usnistgov/OSCAL/actions/runs/3359592310/jobs/5567773731

All Submissions:

• Have you selected the correct base branch per Contributing guidance?
• Have you set "Allow edits and access to secrets by maintainers
  "?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you squashed any non-relevant commits and commit messages? [instructions]
• Do all automated CI/CD checks pass?

By submitting a pull request, you are agreeing to provide this contribution under the CC0 1.0 Universal public domain dedication.

Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you included examples of how to use your new feature(s)?
• Have you updated all OSCAL website and readme documentation affected by the changes you made? Changes to the OSCAL website can be made in the docs/content directory of your branch.

[aj-stein-nist]

@david-waltermire-nist, we likely want to merge this into main or the PR branch for #1518 as this is the last thing holding back that PR from going full green in CI and unbreaking all other PRs with link checking and testing failures as documented in that PR as well.