Fix nb.gv failure during docfx build

Author: AArnott

.github/workflows/docs.yml

@@ -25,6 +25,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
+      with:
+        fetch-depth: 0 # avoid shallow clone so nbgv can do its work.
     - name: ⚙ Install prerequisites
       run: ./init.ps1 -UpgradePrerequisites