Pin dependencies (#298)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/docs_validate.yml

@@ -13,11 +13,11 @@ jobs:
     name: 📚 Doc validation
     runs-on: ubuntu-24.04
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
       with:
         fetch-depth: 0 # avoid shallow clone so nbgv can do its work.
     - name: 🔗 Markup Link Checker (mlc)
-      uses: becheran/[email protected]
+      uses: becheran/mlc@c925f90a9a25e16e4c4bfa29058f6f9ffa9f0d8c # v0.21.0
       with:
         args: --do-not-warn-for-redirect-to https://learn.microsoft.com*,https://dotnet.microsoft.com/*,https://dev.azure.com/*,https://app.codecov.io/* -p docfx -i https://aka.ms/onboardsupport,https://aka.ms/spot,https://msrc.microsoft.com/*,https://www.microsoft.com/msrc*,https://microsoft.com/msrc*
     - name: ⚙ Install prerequisites