Bump http-proxy from 1.17.0 to 1.18.1 in /packages/next-flexible-routes

Bumps [http-proxy](https://github.com/http-party/node-http-proxy) from 1.17.0 to 1.18.1.
- [Release notes](https://github.com/http-party/node-http-proxy/releases)
- [Changelog](https://github.com/http-party/node-http-proxy/blob/master/CHANGELOG.md)
- [Commits](http-party/node-http-proxy@1.17.0...1.18.1)

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

packages/next-flexible-routes/package.json

@@ -67,7 +67,7 @@
     "fp-ts": "^1.15.0",
     "fp-ts-contrib": "^0.0.2",
     "handlebars": "^4.1.2",
-    "http-proxy": "^1.17.0",
+    "http-proxy": "^1.18.1",
     "io-ts": "^1.8.4",
     "jasmine-check": "^1.0.0-rc.0",
     "jest": "^24.8.0",