fix syntax issue in github action

Author: benbariteau

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
         with:
-          python-version: 3.10
+          python-version: '3.10'
       - run: pip install tox
       - run: tox -e ${{ matrix.python }}-${{ matrix.httplib }}
 
@@ -34,6 +34,6 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
         with:
-          python-version: 3.10
+          python-version: '3.10'
       - run: pip install tox
       - run: tox -e ${{ matrix.tox }}