Downgrades flake to 6.1.0

.github/workflows/unit-tests.yaml

@@ -43,7 +43,7 @@ jobs:
         pip install flake8-pytest-importorskip
         pip install --upgrade click==8.0.4
         pip install black==24.4.2
-        pip install flake8==7.0.0
+        pip install flake8==6.1.0
 
     - name: Lint and Format Check with Flake8 and Black
       if: ${{ matrix.python-version == 3.9 }}