Bump express-validator from 2.21.0 to 6.10.0

Bumps [express-validator](https://github.com/express-validator/express-validator) from 2.21.0 to 6.10.0.
- [Release notes](https://github.com/express-validator/express-validator/releases)
- [Commits](express-validator/express-validator@v2.21.0...v6.10.0)

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

Author: dependabot-preview[bot]

package.json

@@ -32,7 +32,7 @@
     "dotenv-safe": "^3.0.0",
     "express": "^4.12.0",
     "express-session": "^1.10.3",
-    "express-validator": "^2.17.1",
+    "express-validator": "^6.10.0",
     "http-auth": "^3.1.0",
     "jade": "^1.9.2",
     "mongoose": "^4.1.5",