ci: pin the action version

Author: zimeg

.github/workflows/tests.yml

@@ -75,7 +75,7 @@ jobs:
           pytest tests/scenario_tests_async/ --junitxml=reports/test_scenario_async.xml
       - name: Send notifications of failing tests
         if: failure() && github.ref == 'refs/heads/main'
-        uses: slackapi/[email protected]
+        uses: slackapi/slack-github-action@b0fa283ad8fea605de13dc3f449259339835fc52 # v2.1.0
         with:
           webhook: ${{ secrets.SLACK_REGRESSION_FAILURES_WEBHOOK_URL }}
           webhook-type: webhook-trigger