Remove 3.9

.github/workflows/pythonpackage.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       max-parallel: 4
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: [3.6, 3.7, 3.8]
 
     steps:
       - uses: actions/checkout@v1
@@ -26,7 +26,5 @@ jobs:
           make typecheck
       - name: Test with pytest
         run: |
-          pip install poetry pytest
-          poetry install
           pip install .
           pytest tests/ -v