YT config update for finch experiment around ACCEPT_CH over TLS

 * Trigger is 'YTCH' connection opt

Note: This change has no effect on runtime behavior until the finch experiment is started.
PiperOrigin-RevId: 384571235
diff --git a/quic/core/crypto/crypto_protocol.h b/quic/core/crypto/crypto_protocol.h
index 43fcd39..6a4f162 100644
--- a/quic/core/crypto/crypto_protocol.h
+++ b/quic/core/crypto/crypto_protocol.h
@@ -410,6 +410,9 @@
                                                  // wire PING (ROWP) on the
                                                  // server side.
 
+// Client Hints triggers.
+const QuicTag kYTCH = TAG('Y', 'T', 'C', 'H');
+
 // Rejection tags
 const QuicTag kRREJ = TAG('R', 'R', 'E', 'J');   // Reasons for server sending