Update kube-prometheus-stack Docker tag to v78.3.1

Author: renovate[bot]

clusters/common/apps/monitoring/app/helmrelease-kube-prometheus-stack.yaml

@@ -8,7 +8,7 @@ spec:
   chart:
     spec:
       chart: kube-prometheus-stack
-      version: 78.2.0 # Use a recent stable version
+      version: 78.3.1 # Use a recent stable version
       sourceRef:
         kind: HelmRepository
         name: prometheus-community # Use prometheus-community repo (OCI or web based on previous steps)