Deprecate --gfe2_reloadable_flag_quic_send_connection_close_on_max_age.

PiperOrigin-RevId: 900153922

quiche/quic/core/crypto/crypto_protocol.h

diff --git a/quiche/quic/core/crypto/crypto_protocol.h b/quiche/quic/core/crypto/crypto_protocol.h
index 4817343..d80cc8a 100644
--- a/quiche/quic/core/crypto/crypto_protocol.h
+++ b/quiche/quic/core/crypto/crypto_protocol.h
@@ -549,9 +549,8 @@
 DEFINE_STATIC_QUIC_TAG(CFLS);  // Enable flow-label-based blackhole avoidance on
                                // the server side when the client sends CFLS.
 
-// Experiment for explicit connection close packet for silent idle timeout
-// from server.
-DEFINE_STATIC_QUIC_TAG(ECCP);
+// Explicit connection close packet for max age timeout from server.
+DEFINE_STATIC_QUIC_TAG(ECCP);  // Deprecated and Default Enabled.
 
 #undef DEFINE_STATIC_QUIC_TAG