Revert "Upgrade pip": already up to date

This reverts commit b6714a0.

Author: echarrod

.github/workflows/tests.yaml

@@ -42,8 +42,6 @@ jobs:
 
       - uses: actions/setup-python@v2.3.1
 
-      - run: python3 -m pip install --upgrade pip
-
       - run: pip install -U setuptools==45
 
       - run: pushd examples/aml && pip install -r requirements.txt && popd