Fix -Wdefaulted-function-deleted warning in qpack

gfe-relnote: compile-only change
PiperOrigin-RevId: 245511621
Change-Id: I8999e5976e8737a10539c7d76f85b8825db2b6e5

quic/core/qpack/value_splitting_header_list.h

diff --git a/quic/core/qpack/value_splitting_header_list.h b/quic/core/qpack/value_splitting_header_list.h
index e47567e..2a8cdf0 100644
--- a/quic/core/qpack/value_splitting_header_list.h
+++ b/quic/core/qpack/value_splitting_header_list.h
@@ -37,7 +37,7 @@
     // Find next '\0' character; update |value_end_| and |header_field_|.
     void UpdateHeaderField();
 
-    const spdy::SpdyHeaderBlock* const header_list_;
+    const spdy::SpdyHeaderBlock* header_list_;
     spdy::SpdyHeaderBlock::const_iterator header_list_iterator_;
     QuicStringPiece::size_type value_start_;
     QuicStringPiece::size_type value_end_;