try formatting payload explicitly as json

Author: diamonwiggins

.github/workflows/embedded-cluster-release-notes.yml

@@ -89,7 +89,7 @@ jobs:
         uses: slackapi/[email protected]
         with:
           webhook: ${{ secrets.EMBEDDED_CLUSTER_RELEASE_NOTES_SLACK_WEBHOOK }}
-          webhook-type: incoming-webhook
+          webhook-type: webhook-trigger
           payload: |
-            version: "${{ github.event.inputs.version }}"
-            pull_request_url: "${{steps.cpr.outputs.pull-request-url}}"
+            "version": "${{ github.event.inputs.version }}",
+            "pull_request_url": "${{steps.cpr.outputs.pull-request-url}}",