ci: Update python-version matrix

Signed-off-by: GitHub <noreply@github.com>

Author: chizhg

.github/workflows/unit.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: [3.7, 3.8, 3.9, '3.10', '3.11']
+        python: ['3.7', '3.8', '3.9', '3.10', '3.11']
     steps:
     - name: Checkout
       uses: actions/checkout@v2