Bump formidable from 1.2.6 to 3.5.1

Bumps [formidable](https://github.com/node-formidable/formidable) from 1.2.6 to 3.5.1.
- [Release notes](https://github.com/node-formidable/formidable/releases)
- [Changelog](https://github.com/node-formidable/formidable/blob/master/CHANGELOG.md)
- [Commits](https://github.com/node-formidable/formidable/commits/v3.5.1)

---
updated-dependencies:
- dependency-name: formidable
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

package.json

@@ -7,7 +7,7 @@
     "ejs": "^3.1.2",
     "eris": "^0.14.0",
     "express": "^4.16.4",
-    "formidable": "^1.2.1",
+    "formidable": "^3.5.1",
     "fs-extra": "^9.0.0",
     "helmet": "^4.0.0",
     "lowdb": "^1.0.0",