update ci

Signed-off-by: Xin Wang <xin.wang@fmr.com>

Author: takojunior

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9, 3.10]
+        python-version: ['3.6', '3.7', '3.8', '3.9', '3.10']
         os: [ubuntu-latest, macos-latest, windows-latest]
     steps:
       - uses: actions/checkout@v3