Fix formatting of packet number length in QuicPacketHeader operator<<

gfe-relnote: n/a (test/debug-only formatting fix)
PiperOrigin-RevId: 288402356
Change-Id: I6dc430c0574963255facecda3ba69bcc8aa083d7

quic/core/quic_packets.cc

diff --git a/quic/core/quic_packets.cc b/quic/core/quic_packets.cc
index 3518f07..4123c27 100644
--- a/quic/core/quic_packets.cc
+++ b/quic/core/quic_packets.cc
@@ -237,7 +237,8 @@
      << (header.source_connection_id_included == CONNECTION_ID_PRESENT
              ? "present"
              : "absent")
-     << "), packet_number_length: " << header.packet_number_length
+     << "), packet_number_length: "
+     << static_cast<int>(header.packet_number_length)
      << ", reset_flag: " << header.reset_flag
      << ", version_flag: " << header.version_flag;
   if (header.version_flag) {