Update security contacts (#5719)

SECURITY_CONTACTS

@@ -1,13 +1,13 @@
 # Defined below are the security contacts for this repo.
 #
-# They are the contact point for the Product Security Team to reach out
+# They are the contact point for the Product Security Committee to reach out
 # to for triaging and handling of incoming issues.
 #
 # The below names agree to abide by the
-# [Embargo Policy](https://github.com/kubernetes/sig-release/blob/master/security-release-process-documentation/security-release-process.md#embargo-policy)
+# [Embargo Policy](https://git.k8s.io/security/private-distributors-list.md#embargo-policy)
 # and will be removed and replaced if they violate that agreement.
 #
 # DO NOT REPORT SECURITY VULNERABILITIES DIRECTLY TO THESE NAMES, FOLLOW THE
 # INSTRUCTIONS AT https://kubernetes.io/security/
 atoms
-mattymo
+mattymo