Remove redundant stream finding code when STOP_SENDING frame is received. QuicSession::OnStopSending() already finds the stream and does staticness checks. We can simplify QuicSession::SendRstStreamInner() by moving the stream book keeping to OnStopSending(). gfe-relnote: protected by disabled v99 flag. PiperOrigin-RevId: 278745064 Change-Id: I3734cff264fdadd58d3dfe50b418fd4c76bd19ce