fix(package): update nodemailer to version 6.4.2

Closes #98

Author: greenkeeper[bot]

package.json

@@ -18,7 +18,7 @@
     "moesif-express": "2.9.7",
     "mysql": "2.17.0",
     "node-telegram-bot-api": "0.30.0",
-    "nodemailer": "5.1.1",
+    "nodemailer": "6.4.2",
     "npm": "6.10.2",
     "password-hash": "1.2.2",
     "qrcode": "^1.3.2",