fix(package): update mocha to version 6.2.2

Closes #100

Author: greenkeeper[bot]

package.json

@@ -14,7 +14,7 @@
     "express": "4.17.1",
     "express-session": "1.16.2",
     "firebase-admin": "8.4.0",
-    "mocha": "6.0.0",
+    "mocha": "6.2.2",
     "moesif-express": "2.9.7",
     "mysql": "2.17.0",
     "node-telegram-bot-api": "0.30.0",