Bump nodemailer from 4.7.0 to 6.9.9

Bumps [nodemailer](https://github.com/nodemailer/nodemailer) from 4.7.0 to 6.9.9.
- [Release notes](https://github.com/nodemailer/nodemailer/releases)
- [Changelog](https://github.com/nodemailer/nodemailer/blob/master/CHANGELOG.md)
- [Commits](nodemailer/nodemailer@v4.7.0...v6.9.9)

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

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

Author: dependabot[bot]

package-lock.json

@@ -37,7 +37,7 @@
     "lodash": "^4.17.11",
     "mongoose": "^5.2.17",
     "morgan": "^1.9.1",
-    "nodemailer": "^4.6.7",
+    "nodemailer": "^6.9.9",
     "nodemailer-smtp-transport": "^2.7.4",
     "prompt-sync": "^4.1.6",
     "q": "^1.5.1",