Bump nodemailer from 4.0.1 to 6.4.16

Bumps [nodemailer](https://github.com/nodemailer/nodemailer) from 4.0.1 to 6.4.16.
- [Release notes](https://github.com/nodemailer/nodemailer/releases)
- [Changelog](https://github.com/nodemailer/nodemailer/blob/master/CHANGELOG.md)
- [Commits](nodemailer/nodemailer@v4.0.1...v6.4.16)

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

Author: dependabot[bot]

package-lock.json

@@ -72,7 +72,7 @@
     "moment-timezone": "~0.5.31",
     "morgan": "~1.9.0",
     "multer": "~1.3.1",
-    "nodemailer": "~4.0.1",
+    "nodemailer": "~6.4.16",
     "nodemailer-mailgun-transport": "~1.4.0",
     "package-lock": "~1.0.3",
     "pg-promise": "~10.6.1",