Bump jsonwebtoken from 8.3.0 to 8.4.0

Bumps [jsonwebtoken](https://github.com/auth0/node-jsonwebtoken) from 8.3.0 to 8.4.0.
- [Release notes](https://github.com/auth0/node-jsonwebtoken/releases)
- [Changelog](https://github.com/auth0/node-jsonwebtoken/blob/master/CHANGELOG.md)
- [Commits](auth0/node-jsonwebtoken@v8.3.0...v8.4.0)

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

Author: dependabot-support

package-lock.json

@@ -25,7 +25,7 @@
     "express-validator": "^5.2.0",
     "express-winston": "^2.5.1",
     "handlebars": "^4.0.12",
-    "jsonwebtoken": "^8.1.0",
+    "jsonwebtoken": "^8.4.0",
     "memory-cache": "^0.2.0",
     "mongoose": "^5.1.0",
     "multer": "^1.4.1",