remove pip upgrade

.github/workflows/testing.yml

@@ -20,10 +20,6 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
 
-      - name: Update pip
-        run: |
-          pip install --upgrade pip
-
       - name: Install PyTorch ${{ matrix.torch-version }}
         run: |
           pip install torch==${{ matrix.torch-version}}+cpu -f https://download.pytorch.org/whl/torch_stable.html