Update dependency https://github.com/istio/istio to v1.15.4

Author: renovate[bot]

distribution/argocd-applications/istio-operator.yaml

@@ -7,7 +7,7 @@ spec:
   project: default
   source:
     repoURL: https://github.com/istio/istio
-    targetRevision: 1.15.2
+    targetRevision: 1.15.4
     path: manifests/charts/istio-operator
     helm:
       parameters: