chore(deps): bump sequelize from 5.10.1 to 5.15.1

Bumps [sequelize](https://github.com/sequelize/sequelize) from 5.10.1 to 5.15.1.
- [Release notes](https://github.com/sequelize/sequelize/releases)
- [Commits](sequelize/sequelize@v5.10.1...v5.15.1)

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

Author: dependabot[bot]

package-lock.json

@@ -60,7 +60,7 @@
     "redux": "^4.0.1",
     "redux-logger": "^3.0.6",
     "redux-thunk": "^2.3.0",
-    "sequelize": "^5.3.1",
+    "sequelize": "^5.15.1",
     "socket.io": "^2.2.0"
   },
   "devDependencies": {