Bump sequelize from 4.35.5 to 5.15.1

Bumps [sequelize](https://github.com/sequelize/sequelize) from 4.35.5 to 5.15.1.
- [Release notes](https://github.com/sequelize/sequelize/releases)
- [Commits](sequelize/sequelize@v4.35.5...v5.15.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -31,7 +31,7 @@
     "lodash": "^4.17.4",
     "mysql2": "^1.5.1",
     "protobufjs": "^6.8.0",
-    "sequelize": "^4.22.6",
+    "sequelize": "^5.15.1",
     "winston": "^3.0.0-rc1",
     "moment": "^2.22.2",
     "mongoose": "^5.2.3"