Don't send Slack notifications for PR build failures

Author: ceedubs

.github/workflows/cloud-client-tests.yml

@@ -58,7 +58,7 @@ jobs:
           apt-get update && apt-get -y install gettext-base
           ./run-tests.sh
       - name: Slack notification
-        if: ${{ failure() }}
+        if: ${{ failure() && github.event_name != 'pull_request' }}
         uses: slackapi/slack-github-action@485a9d42d3a73031f12ec201c457e2162c45d02d # v2.0.0
         with:
           method: chat.postMessage