build(deps): bump rate-limiter-flexible in /apps/OpenSignServer

Bumps [rate-limiter-flexible](https://github.com/animir/node-rate-limiter-flexible) from 7.4.0 to 8.1.0.
- [Release notes](https://github.com/animir/node-rate-limiter-flexible/releases)
- [Commits](animir/node-rate-limiter-flexible@v7.4.0...v8.1.0)

---
updated-dependencies:
- dependency-name: rate-limiter-flexible
  dependency-version: 8.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

apps/OpenSignServer/package-lock.json

@@ -51,7 +51,7 @@
     "pdf-lib": "^1.17.1",
     "posthog-node": "^5.9.1",
     "qrcode": "^1.5.4",
-    "rate-limiter-flexible": "^7.4.0",
+    "rate-limiter-flexible": "^8.1.0",
     "sharp": "^0.34.4",
     "speakeasy": "^2.0.0",
     "ws": "^8.18.3"