Bump express from 4.17.1 to 4.17.3

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:development
...

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

Author: dependabot[bot]

package.json

@@ -62,7 +62,7 @@
         "eslint-plugin-jsx-a11y": "^2.2.3",
         "eslint-plugin-prettier": "^3.1.0",
         "eslint-plugin-react": "^6.6.0",
-        "express": "^4.13.4",
+        "express": "^4.17.3",
         "extract-text-webpack-plugin": "^1.0.1",
         "html-webpack-plugin": "^2.24.1",
         "jsdom": "^9.2.0",