Update difficulty for 720. Longest Word in Dictionary (seanprashad#109)

Author: td31

src/data/index.js

@@ -2027,7 +2027,7 @@ const questions = [
  name: 'Longest Word in Dictionary',
  url: 'https://leetcode.com/problems/longest-word-in-dictionary/',
  pattern: ['Trie'],
- difficulty: 'Easy',
+ difficulty: 'Medium',
  premium: false,
  companies: ['Goldman Sachs', 'Amazon'],
  },