message: Fix image to be Max
diff: @@ -1658,7 +1658,7 @@ If the maximum is empty for a given segment ID `i`, it outputs the smallest poss
  `output[i] = numeric_limits<T>::min()`.
  <div style="width:70%; margin:auto; margin-bottom:10px; margin-top:20px;">
  -<img style="width:100%" src="https://www.tensorflow.org/images/UnsortedSegmentSum.png" alt>
  +<img style="width:100%" src="https://www.tensorflow.org/images/UnsortedSegmentMax.png" alt>
  </div>
  segment_ids: A 1-D tensor whose rank is equal to the rank of `data`'s
  