Fixed GHA

Author: azmeuk

.github/workflows/main.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: [3.6, 3.7, 3.8, 3.9, 3.10]
+        python: ["3.6", "3.7", "3.8", "3.9", "3.10"]
 
     steps:
       - uses: actions/checkout@v2