update pinned version to fix py3.4 compatibility

update pinned version to fix py3.4 compatibility

Author: carolabadeer

.github/workflows/UnitTesting.yaml

@@ -36,7 +36,7 @@ jobs:
           python-version: ${{ env[matrix.python-version] }}
 
       - name: Install tox
-        run: pip install tox==3.27.1 -U tox-factor
+        run: pip install tox <= 3.27.1 -U tox-factor
 
       - name: Cache tox environment
         # Preserves .tox directory between runs for faster installs