Update sequelize to version 5.21.5

Author: depfu[bot]

package.json

@@ -10,7 +10,7 @@
   "dependencies": {
     "cheerio": "^0.17.0",
     "lodash.flatten": "^2.4.1",
-    "sequelize": "^2.0.0",
+    "sequelize": "^5.21.5",
     "sqlite3": "^3.0.5"
   },
   "devDependencies": {},