[gh actions] Move coveralls to Python 3.10

Author: mpsonntag

.github/workflows/run-tests.yml

@@ -100,10 +100,10 @@ jobs:
     runs-on: [ubuntu-latest]
     steps:
       - uses: actions/checkout@v2
-      - name: Setup Python 3.8
+      - name: Setup Python 3.10
         uses: actions/setup-python@v2
         with:
-          python-version: "3.8"
+          python-version: "3.10"
       - name: Display Python version
         run: python -c "import sys; print(sys.version)"
       - name: Install dependencies