CI: github no longer checks whitelisted actions this way (#11507)

* CI: github no longer checks whitelisted actions this way

* CI: actually this one is needed and no one knows it's related to a Markdown Link Check

substrate/.github/allowed-actions.js

-// This is a whitelist of GitHub Actions that are approved for use in this project.
-// If a new or existing workflow file is updated to use an action or action version
-// not listed here, CI will fail.
-
-module.exports = [
-    'gaurav-nelson/github-action-markdown-link-check@7481451f70251762f149d69596e3e276ebf2b236', // gaurav-nelson/github-action-markdown-link-check@v1.0.8
-]