Bump nodemailer from 3.1.8 to 6.6.1

Bumps [nodemailer](https://github.com/nodemailer/nodemailer) from 3.1.8 to 6.6.1.
- [Release notes](https://github.com/nodemailer/nodemailer/releases)
- [Changelog](https://github.com/nodemailer/nodemailer/blob/master/CHANGELOG.md)
- [Commits](nodemailer/nodemailer@v3.1.8...v6.6.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -95,7 +95,7 @@
     "node-sass": "^4.14.1",
     "node-sass-middleware": "^0.11.0",
     "node-webvtt": "^1.9.3",
-    "nodemailer": "^3.1.7",
+    "nodemailer": "^6.6.1",
     "nodemailer-mailgun-transport": "^1.4.0",
     "nodemon": "^2.0.20",
     "object-sizeof": "^1.3.1",