message: Remove assert in TxBuffer::mark_as_lost()
  It is not valid to assert this, because this can occur if the highest range
  was unmarked (so it will be a candidate for retransmission) and then we
  attempt to unmark it again, maybe if a PTO included the same range but
  the PTO was lost.
  fixes
diff: @@ -350,7 +350,6 @@ impl TxBuffer {
  }
  pub fn mark_as_lost(&mut self, offset: u64, len: usize) {
  - debug_assert!(self.ranges.highest_offset() >= offset + len as u64);
  self.ranges.unmark_range(offset, len)
  }
  