quic: fix typo in code comment

successfull -> successful

PR-URL: #35308
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Zeyu Yang <himself65@outlook.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

src/quic/node_quic_session.cc

@@ -1984,7 +1984,7 @@ bool QuicSession::OpenUnidirectionalStream(int64_t* stream_id) {
   return ngtcp2_conn_open_uni_stream(connection(), stream_id, nullptr) == 0;
 }
 
-// When ngtcp2 receives a successfull response to a PATH_CHALLENGE,
+// When ngtcp2 receives a successful response to a PATH_CHALLENGE,
 // it will trigger the OnPathValidation callback which will, in turn
 // invoke this. There's really nothing to do here but update stats and
 // and optionally notify the javascript side if there is a handler registered.