fix: package.json & package-lock.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://dev.snyk.io/vuln/SNYK-JS-MOMENT-2944238
- https://dev.snyk.io/vuln/SNYK-JS-MOMENT-2440688

Author: snyk-bot

package.json

@@ -152,7 +152,7 @@
     "sanitize-filename": "^1.6.3",
     "sanitize-html": "1.4.2",
     "semver": "^7.3.2",
-    "sequelize": "^5.22.3",
+    "sequelize": "^6.1.0",
     "sequelize-noupdate-attributes": "^1.0.0",
     "serve-index": "^1.9.1",
     "socket.io": "^2.3.0",