Updated Github Actions workflow to use Tox through pip instead of the platform version.

.github/workflows/tox.yaml

@@ -17,8 +17,8 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip
-          pip install -U codecov coveralls flake8 mypy pylint pytest tox
+          python3 -m pip install --upgrade pip
+          python3 -m pip install -U codecov coveralls flake8 mypy pylint pytest tox
       - name: Run Tox
         run: |
-          tox
+          python3 -m tox