message: Update word-search-ii.cpp
diff: -// Time: O(m * n * h), h is height of trie
  -// Space: O(26^h)
  +// 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 Solution {
  private:
  