message: Update word-search-ii.py
diff: -# Time: O(m * n * l)
  -# Space: O(l)
  +# Time: O(m * n * 4 * 3^(h - 1)) ~= O(m * n * 3^h), h is the height of trie
  +# Space: O(t), t is the number of nodes in trie
  class TrieNode(object):
  # Initialize your data structure here.
  