chore(ci): run tests against Python 3.10

Author: mkniewallner

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10.0-rc.2"]
+        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10"]
         os: [ubuntu-latest, ubuntu-18.04, macos-latest, windows-latest]
 
     steps:
@@ -53,11 +53,6 @@ jobs:
           python -m pip install --upgrade pip
           python -m pip install --upgrade poetry
 
-      # New poetry installer doesn't work well with Python 3.10 (see https://github.com/python-poetry/poetry/issues/4210).
-      - name: Use legacy poetry installer
-        if: startsWith(matrix.python-version, '3.10')
-        run: poetry config experimental.new-installer false
-
       - name: Install dependencies
         run: poetry install