chore(deps): bump sequelize from 6.21.2 to 6.37.8 in /backend

Bumps [sequelize](https://github.com/sequelize/sequelize) from 6.21.2 to 6.37.8.
- [Release notes](https://github.com/sequelize/sequelize/releases)
- [Changelog](https://github.com/sequelize/sequelize/blob/main/CHANGELOG.md)
- [Commits](sequelize/sequelize@v6.21.2...v6.37.8)

---
updated-dependencies:
- dependency-name: sequelize
  dependency-version: 6.37.8
  dependency-type: direct:production
...

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

Author: dependabot[bot]

backend/package.json

@@ -128,7 +128,7 @@
     "pg": "^8.7.3",
     "pg-promise": "^11.4.3",
     "sanitize-html": "^2.7.1",
-    "sequelize": "6.21.2",
+    "sequelize": "6.37.8",
     "sequelize-cli-typescript": "^3.2.0-c",
     "slack-block-builder": "^2.7.2",
     "socket.io": "^4.5.4",