Deprecate --gfe2_reloadable_flag_quic_discard_packets_with_invalid_cid

PiperOrigin-RevId: 392474439
diff --git a/quic/core/quic_dispatcher.cc b/quic/core/quic_dispatcher.cc
index 11f4bcd..a7345ea 100644
--- a/quic/core/quic_dispatcher.cc
+++ b/quic/core/quic_dispatcher.cc
@@ -512,19 +512,16 @@
     return true;
   }
 
-  if (GetQuicReloadableFlag(quic_discard_packets_with_invalid_cid)) {
-    QUIC_RELOADABLE_FLAG_COUNT(quic_discard_packets_with_invalid_cid);
-    if (packet_info.version_flag && packet_info.version.IsKnown() &&
-        !QuicUtils::IsConnectionIdLengthValidForVersion(
-            server_connection_id.length(),
-            packet_info.version.transport_version)) {
-      QUIC_DLOG(INFO) << "Packet with destination connection ID "
-                      << server_connection_id << " is invalid with version "
-                      << packet_info.version;
-      // Drop the packet silently.
-      QUIC_CODE_COUNT(quic_dropped_invalid_initial_connection_id);
-      return true;
-    }
+  if (packet_info.version_flag && packet_info.version.IsKnown() &&
+      !QuicUtils::IsConnectionIdLengthValidForVersion(
+          server_connection_id.length(),
+          packet_info.version.transport_version)) {
+    QUIC_DLOG(INFO) << "Packet with destination connection ID "
+                    << server_connection_id << " is invalid with version "
+                    << packet_info.version;
+    // Drop the packet silently.
+    QUIC_CODE_COUNT(quic_dropped_invalid_initial_connection_id);
+    return true;
   }
 
   // Packets with connection IDs for active connections are processed
diff --git a/quic/core/quic_dispatcher_test.cc b/quic/core/quic_dispatcher_test.cc
index e713fe7..e927cda 100644
--- a/quic/core/quic_dispatcher_test.cc
+++ b/quic/core/quic_dispatcher_test.cc
@@ -1127,7 +1127,6 @@
 
 TEST_P(QuicDispatcherTestAllVersions,
        DropPacketWithKnownVersionAndInvalidInitialConnectionId) {
-  SetQuicReloadableFlag(quic_discard_packets_with_invalid_cid, true);
   CreateTimeWaitListManager();
 
   QuicSocketAddress server_address;
diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index 85fb592..a9d584f 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -87,8 +87,6 @@
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_use_active_cid_for_session_lookup, true)
 // If true, pass the received PATH_RESPONSE payload to path validator to move forward the path validation.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_pass_path_response_to_validator, true)
-// If true, quic dispatcher discards packets with invalid server connection ID.
-QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_discard_packets_with_invalid_cid, true)
 // If true, quic dispatcher supports one connection to use multiple connection IDs. 
 QUIC_FLAG(FLAGS_quic_restart_flag_quic_dispatcher_support_multiple_cid_per_connection_v2, true)
 // If true, receiving server push stream will trigger QUIC connection close.