improve python matrix

Author: caesar0301

.github/workflows/python-package.yml

@@ -23,7 +23,6 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
-        python -m pip install --upgrade pip
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
         if [ -f requirements-t-pre37.txt ]; then pip install -r requirements-t-pre37.txt; fi
     - name: Test with nosetest