Fix Windows virtual environment activation in CI workflows (#9420)

.github/actions/restore-python/action.yml

@@ -41,7 +41,7 @@ runs:
       shell: bash
       run: |
         python -m venv venv
-        ./venv/Scripts/activate
+        source ./venv/Scripts/activate
         python --version
         pip install -r requirements.txt -r requirements_test.txt
         pip install -e .