Update url for nightly builds. (#1100)

.github/workflows/torch_nightly.yml

@@ -36,7 +36,7 @@ jobs:
         python -m pip install --upgrade pip
         pip install -r requirements/requirements.txt
         pip install -r requirements/requirements.dev.txt
-        pip3 install --pre torch -f https://download.pytorch.org/whl/nightly/cpu/torch_nightly.html --upgrade
+        pip install --pre torch --index-url https://download.pytorch.org/whl/nightly/cpu --upgrade
     - name: Print torch build
       run: pip list | grep torch
     - name: Unit tests