chore(deps): update dependency cert-manager/cert-manager to v1.18.4

Author: renovate[bot]

cert-manager/plugindefinition.yaml

@@ -14,7 +14,7 @@ spec:
   helmChart:
     name: cert-manager
     repository: oci://ghcr.io/cloudoperators/greenhouse-extensions/charts
-    version: 1.18.2
+    version: 1.18.4
   options:
     - name: cert-manager.installCRDs
       description: Whether to install CRDs