Bump express from 4.17.1 to 4.17.3 in /netlify-express

Bumps [express](https://github.com/expressjs/express) from 4.17.1 to 4.17.3.
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/master/History.md)
- [Commits](expressjs/express@4.17.1...4.17.3)

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

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

Author: dependabot[bot]

netlify-express/package.json

@@ -18,7 +18,7 @@
   },
   "dependencies": {
     "body-parser": "^1.19.0",
-    "express": "^4.17.1",
+    "express": "^4.17.3",
     "serverless-http": "^2.3.2"
   },
   "devDependencies": {