Addresses import compile fail

external/com_github_google_quiche/quiche/quic/test_tools/quic_test_utils.h:2013:3: error: 'const' type qualifier on return type has no effect [-Werror,-Wignored-qualifiers]
  const QuicEcnCodepoint last_ecn_sent() const { return last_ecn_sent_; }

PiperOrigin-RevId: 523720260

quiche/quic/test_tools/quic_test_utils.h

diff --git a/quiche/quic/test_tools/quic_test_utils.h b/quiche/quic/test_tools/quic_test_utils.h
index 56cf981..2835ac1 100644
--- a/quiche/quic/test_tools/quic_test_utils.h
+++ b/quiche/quic/test_tools/quic_test_utils.h
@@ -2010,7 +2010,7 @@
     return last_write_peer_address_;
   }
 
-  const QuicEcnCodepoint last_ecn_sent() const { return last_ecn_sent_; }
+  QuicEcnCodepoint last_ecn_sent() const { return last_ecn_sent_; }
 
  private:
   char* AllocPacketBuffer();