chore: Update grafana/shared-workflows digest to a4e8131 (#1121)

Co-authored-by: grafanarenovatebot[bot] <146220760+grafanarenovatebot[bot]@users.noreply.github.com>

.github/workflows/build_and_publish.yaml

@@ -278,7 +278,7 @@ jobs:
       - name: Trigger argo workflow
         # trigger-argo-workflow hasn't been released yet, so we're using a
         # commit hash to reference it that has no associated version.
-        uses: grafana/shared-workflows/actions/trigger-argo-workflow@5b45f78444eda7dd8b4e08d99bc91e55aa3cb007
+        uses: grafana/shared-workflows/actions/trigger-argo-workflow@a4e8131f2eb342771e1c5564fd934444767c04b0
         with:
           namespace: synthetic-monitoring-cd
           workflow_template: deploy-${{ needs.preflight.outputs.repo_name }}