Bump node-fetch from 2.6.1 to 2.6.7 in /backend

Bumps [node-fetch](https://github.com/node-fetch/node-fetch) from 2.6.1 to 2.6.7.
- [Release notes](https://github.com/node-fetch/node-fetch/releases)
- [Commits](https://github.com/node-fetch/node-fetch/compare/v2.6.1...v2.6.7)

---
updated-dependencies:
- dependency-name: node-fetch
  dependency-type: direct:production
...

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backend/package.json

@@ -50,7 +50,7 @@
     "moment": "^2.29.1",
     "mongodb": "^3.6.9",
     "multer": "^1.4.2",
-    "node-fetch": "^2.6.1",
+    "node-fetch": "^2.6.7",
     "node-id3": "^0.1.14",
     "nodemon": "^2.0.7",
     "passport": "^0.4.1",