Fix Git LFS authentication for docs workflow

Author: bhimrazy

.github/workflows/docs-build.yml

@@ -70,6 +70,11 @@ jobs:
           # only Pytorch has/uses notebooks
           submodules: ${{ matrix.pkg-name == 'pytorch' }}
           lfs: ${{ matrix.pkg-name == 'pytorch' }}
+      - name: Setup Git LFS credentials
+        if: ${{ matrix.pkg-name == 'pytorch' }}
+        run: |
+          git config --global credential.helper store
+          echo "https://$GITHUB_ACTOR:[email protected]" > ~/.git-credentials
       - uses: actions/setup-python@v6
         with:
           python-version: "3.10"