Bump fluxcd/kustomize-controller to latest release

Author: eks-distro-pr-bot

UPSTREAM_PROJECTS.yaml

@@ -113,7 +113,7 @@ projects:
             go_version: "1.25"
       - name: kustomize-controller
         versions:
-          - tag: v1.7.0
+          - tag: v1.7.3
             go_version: "1.25"
       - name: notification-controller
         versions: