Remove unused connect-udp-version

This is no longer used now that we only support RFC 9298 and not earlier drafts.

PiperOrigin-RevId: 606360801

quiche/quic/masque/masque_client_session.cc

diff --git a/quiche/quic/masque/masque_client_session.cc b/quiche/quic/masque/masque_client_session.cc
index 842e454..7e5dfdd 100644
--- a/quiche/quic/masque/masque_client_session.cc
+++ b/quiche/quic/masque/masque_client_session.cc
@@ -169,7 +169,6 @@
   headers[":scheme"] = scheme;
   headers[":authority"] = authority;
   headers[":path"] = canonicalized_path;
-  headers["connect-udp-version"] = "12";
   AddAdditionalHeaders(headers, url);
   QUIC_DVLOG(1) << "Sending request headers: " << headers.DebugString();
   size_t bytes_sent =