Deprecate unused field `AT_PUBLIC_METADATA_VERIFIED_KEY_TYPE`.

PiperOrigin-RevId: 529548568

quiche/blind_sign_auth/proto/key_services.proto

diff --git a/quiche/blind_sign_auth/proto/key_services.proto b/quiche/blind_sign_auth/proto/key_services.proto
index 343fea8..ab183c5 100644
--- a/quiche/blind_sign_auth/proto/key_services.proto
+++ b/quiche/blind_sign_auth/proto/key_services.proto
@@ -20,8 +20,8 @@
 
 // Indicates client's desired or capable key support.
 enum KeyType {
+  reserved 3;
   UNKNOWN_KEY_TYPE = 0;
   ZINC_KEY_TYPE = 1;
   AT_PUBLIC_METADATA_KEY_TYPE = 2;
-  AT_PUBLIC_METADATA_VERIFIED_KEY_TYPE = 3;
 }