Remove now useless QUIC method AdjustErrorForVersion() which has been a no-op for some time.

net/quic/core/quic_protocol.cc

Index: net/quic/core/quic_protocol.cc
diff --git a/net/quic/core/quic_protocol.cc b/net/quic/core/quic_protocol.cc
index adf845e23e8f1bc3be5267cfd482fb23398a10cf..32ad09b6268a98c2b0443dc02653fd96be556f54 100644
--- a/net/quic/core/quic_protocol.cc
+++ b/net/quic/core/quic_protocol.cc
@@ -337,11 +337,6 @@ QuicAckFrame::QuicAckFrame(const QuicAckFrame& other) = default;
 
 QuicAckFrame::~QuicAckFrame() {}
 
-QuicRstStreamErrorCode AdjustErrorForVersion(QuicRstStreamErrorCode error_code,
-                                             QuicVersion /*version*/) {
-  return error_code;
-}
-
 QuicRstStreamFrame::QuicRstStreamFrame()
     : stream_id(0), error_code(QUIC_STREAM_NO_ERROR), byte_offset(0) {}