Bump sequelize from 4.42.0 to 5.15.1 in /example

Bumps [sequelize](https://github.com/sequelize/sequelize) from 4.42.0 to 5.15.1.
- [Release notes](https://github.com/sequelize/sequelize/releases)
- [Commits](sequelize/sequelize@v4.42.0...v5.15.1)

---
updated-dependencies:
- dependency-name: sequelize
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

example/package-lock.json

@@ -9,7 +9,7 @@
   "author": "",
   "license": "MIT",
   "dependencies": {
-    "sequelize": "^4.42.0",
+    "sequelize": "^5.15.1",
     "sqlite3": "^4.0.4"
   }
 }