Upadte toc

Author: cici37

keps/sig-api-machinery/3488-cel-admission-control/README.md

@@ -80,6 +80,7 @@
   - [Graduation Criteria](#graduation-criteria)
     - [Alpha](#alpha)
     - [Beta](#beta)
+- [GA](#ga)
   - [Upgrade / Downgrade Strategy](#upgrade--downgrade-strategy)
   - [Version Skew Strategy](#version-skew-strategy)
 - [Production Readiness Review Questionnaire](#production-readiness-review-questionnaire)