ci: try to avoid random test failures

.github/workflows/ci.yml

@@ -36,8 +36,8 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install -r requirements-dev.txt
+          pip install flake8 pytest pytest-mock pytest-cov mypy types-protobuf
-          pip install .
+          pip install --use-pep517 -r requirements.txt
       - name: Lint with flake8
         run: |
           # stop the build if there are Python syntax errors or undefined names