Fix QUIC warnings in preparation for enabling them

gfe-relnote: n/a, compilation-only change
PiperOrigin-RevId: 253893322
Change-Id: I15917a1c5b325922850086277cfad5e3b4da20a4
diff --git a/quic/core/quic_error_codes.h b/quic/core/quic_error_codes.h
index 3de93f6..34019de 100644
--- a/quic/core/quic_error_codes.h
+++ b/quic/core/quic_error_codes.h
@@ -352,7 +352,7 @@
 }
 
 QUIC_EXPORT_PRIVATE inline std::string HistogramEnumDescription(
-    QuicErrorCode dummy) {
+    QuicErrorCode /*dummy*/) {
   return "cause";
 }