Update TOC

Author: jpbetz

keps/sig-api-machinery/4153-declarative-validation/README.md

@@ -129,6 +129,7 @@ tags, and then generate with `hack/update-toc.sh`.
   - [Test Plan](#test-plan)
       - [Prerequisite testing updates](#prerequisite-testing-updates)
       - [Unit tests](#unit-tests)
+      - [Runtime verification testing](#runtime-verification-testing)
       - [Integration tests](#integration-tests)
       - [e2e tests](#e2e-tests)
   - [Graduation Criteria](#graduation-criteria)