monitoring: Update Helm release prometheus-blackbox-exporter to v9.4.0

Author: renovate85-bot[bot]

system/monitoring/kustomization.yaml

@@ -14,7 +14,7 @@ helmCharts:
     releaseName: monitoring
     repo: https://prometheus-community.github.io/helm-charts
     valuesFile: blackbox-exporter-values.yaml
-    version: 9.3.0
+    version: 9.4.0
   - name: prometheus-smartctl-exporter
     namespace: monitoring
     releaseName: monitoring