build(deps): bump undici from 5.22.1 to 5.28.2 in /backend

Bumps [undici](https://github.com/nodejs/undici) from 5.22.1 to 5.28.2.
- [Release notes](https://github.com/nodejs/undici/releases)
- [Commits](https://github.com/nodejs/undici/compare/v5.22.1...v5.28.2)

---
updated-dependencies:
- dependency-name: undici
  dependency-type: indirect
...

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

backend/package-lock.json

@@ -327,6 +327,14 @@
         "node": ">=16.9.0"
       }
     },
+    "node_modules/@fastify/busboy": {
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/@fastify/busboy/-/busboy-2.1.0.tgz",
+      "integrity": "sha512-+KpH+QxZU7O4675t3mnkQKcZZg56u+K/Ct2K+N2AZYNVK8kyeo/bI18tI8aPm3tvNNRyTWfj6s5tnGNlcbQRsA==",
+      "engines": {
+        "node": ">=14"
+      }
+    },
     "node_modules/@jest/types": {
       "version": "24.9.0",
       "dev": true,
@@ -8711,10 +8719,11 @@
       "license": "Apache-2.0"
     },
     "node_modules/undici": {
-      "version": "5.22.1",
+      "version": "5.28.2",
-      "license": "MIT",
+      "resolved": "https://registry.npmjs.org/undici/-/undici-5.28.2.tgz",
+      "integrity": "sha512-wh1pHJHnUeQV5Xa8/kyQhO7WFa8M34l026L5P/+2TYiakvGy5Rdc8jWZVyG7ieht/0WgJLEd3kcU5gKx+6GC8w==",
       "dependencies": {
-        "busboy": "^1.6.0"
+        "@fastify/busboy": "^2.0.0"
       },
       "engines": {
         "node": ">=14.0"