Bump follow-redirects from 1.14.8 to 1.15.6 in /backend

Bumps [follow-redirects](https://github.com/follow-redirects/follow-redirects) from 1.14.8 to 1.15.6.
- [Release notes](https://github.com/follow-redirects/follow-redirects/releases)
- [Commits](https://github.com/follow-redirects/follow-redirects/compare/v1.14.8...v1.15.6)

---
updated-dependencies:
- dependency-name: follow-redirects
  dependency-type: indirect
...

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

backend/package-lock.json

@@ -1873,9 +1873,9 @@
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     },
     "node_modules/follow-redirects": {
-      "version": "1.14.8",
-      "resolved": "https://registry.npmjs.org/follow-redirects/-/follow-redirects-1.14.8.tgz",
-      "integrity": "sha512-1x0S9UVJHsQprFcEC/qnNzBLcIxsjAV905f/UkQxbclCsoTWlacCNOpQa/anodLl2uaEKFhfWOvM2Qg77+15zA==",
+      "version": "1.15.6",
+      "resolved": "https://registry.npmjs.org/follow-redirects/-/follow-redirects-1.15.6.tgz",
+      "integrity": "sha512-wWN62YITEaOpSK584EZXJafH1AGpO8RVgElfkuXbTOrPX4fIfOyEpW/CsiNd8JdYrAoOvafRTOEnvsO++qCqFA==",
       "funding": [
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           "type": "individual",