chore(deps): update module github.com/fluxcd/kustomize-controller/api to v1.9.0

Author: renovate[bot]

go.mod

@@ -4,7 +4,7 @@ go 1.25.0
 
 require (
 	github.com/fluxcd/helm-controller/api v1.5.5
-	github.com/fluxcd/kustomize-controller/api v1.8.5
+	github.com/fluxcd/kustomize-controller/api v1.9.0
 	github.com/spf13/cobra v1.10.2
 	github.com/stretchr/testify v1.11.1
 	gotest.tools/v3 v3.5.2