Negotiate RFC version of H3 Datagrams for WebTransport

This is a preparation to update Chromium side.
https://crbug.com/1426752

PiperOrigin-RevId: 521955882

quiche/quic/tools/quic_simple_server_session.h

diff --git a/quiche/quic/tools/quic_simple_server_session.h b/quiche/quic/tools/quic_simple_server_session.h
index bcb0936..bceb4e5 100644
--- a/quiche/quic/tools/quic_simple_server_session.h
+++ b/quiche/quic/tools/quic_simple_server_session.h
@@ -71,7 +71,7 @@
   }
   HttpDatagramSupport LocalHttpDatagramSupport() override {
     if (ShouldNegotiateWebTransport()) {
-      return HttpDatagramSupport::kDraft04;
+      return HttpDatagramSupport::kRfcAndDraft04;
     }
     return QuicServerSessionBase::LocalHttpDatagramSupport();
   }