Bump send and express in /juice-balancer

Bumps [send](https://github.com/pillarjs/send) to 0.19.0 and updates ancestor dependency [express](https://github.com/expressjs/express). These dependencies need to be updated together.


Updates `send` from 0.18.0 to 0.19.0
- [Release notes](https://github.com/pillarjs/send/releases)
- [Changelog](https://github.com/pillarjs/send/blob/master/HISTORY.md)
- [Commits](pillarjs/send@0.18.0...0.19.0)

Updates `express` from 4.20.0 to 4.21.0
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/4.21.0/History.md)
- [Commits](expressjs/express@4.20.0...4.21.0)

---
updated-dependencies:
- dependency-name: send
  dependency-type: indirect
- dependency-name: express
  dependency-type: direct:production
...

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

juice-balancer/package.json

@@ -18,7 +18,7 @@
     "cookie": "^0.6.0",
     "cookie-parser": "^1.4.6",
     "crypto-random-string": "^3.3.1",
-    "express": "^4.20.0",
+    "express": "^4.21.0",
     "express-joi-validation": "^5.0.1",
     "http-proxy": "^1.18.1",
     "lodash": "^4.17.21",