Fix QUIC_EXPORT_PRIVATE compilation on Windows

QUIC_EXPORT_PRIVATE is a no-op in google3

gfe-relnote: n/a, Chromium-only change
PiperOrigin-RevId: 276429628
Change-Id: Ib3da7917dc0cc7a618045fab0a6eae6ce459741d
diff --git a/quic/core/quic_stream_send_buffer.h b/quic/core/quic_stream_send_buffer.h
index f3b799c..1bccd0f 100644
--- a/quic/core/quic_stream_send_buffer.h
+++ b/quic/core/quic_stream_send_buffer.h
@@ -50,8 +50,7 @@
   // Length of this pending retransmission.
   QuicByteCount length;
 
-  QUIC_EXPORT_PRIVATE bool operator==(
-      const StreamPendingRetransmission& other) const;
+  bool operator==(const StreamPendingRetransmission& other) const;
 };
 
 // QuicStreamSendBuffer contains a list of QuicStreamDataSlices. New data slices