Update Helm release sealed-secrets to v2.18.3

Author: renovate[bot]

infra/argo-apps/sealed-secrets.yaml

@@ -8,7 +8,7 @@ spec:
   source:
     chart: sealed-secrets
     repoURL: https://bitnami-labs.github.io/sealed-secrets
-    targetRevision: 2.18.0
+    targetRevision: 2.18.3
   destination:
     namespace: sealed-secrets
     server: https://kubernetes.default.svc