Add comment about QUIC_CRYPTO deprecation.

PiperOrigin-RevId: 343928627
Change-Id: I30a359de8e4eb950c8419592d031d664fce79e12

quic/core/quic_versions.h

diff --git a/quic/core/quic_versions.h b/quic/core/quic_versions.h
index c29b715..c8f6718 100644
--- a/quic/core/quic_versions.h
+++ b/quic/core/quic_versions.h
@@ -151,6 +151,8 @@
     QuicTransportVersion transport_version);
 
 // The crypto handshake protocols that can be used with QUIC.
+// We are planning on eventually deprecating PROTOCOL_QUIC_CRYPTO in favor of
+// PROTOCOL_TLS1_3.
 enum HandshakeProtocol {
   PROTOCOL_UNSUPPORTED,
   PROTOCOL_QUIC_CRYPTO,