Update ci.yml

3.7 (not supported anymore) -> 3.9

Author: MarioKrenn6240

.github/workflows/ci.yml

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