fix: upgrade mysql2 from 3.2.0 to 3.9.7

Snyk has created this PR to upgrade mysql2 from 3.2.0 to 3.9.7.

See this package in npm:
mysql2

See this project in Snyk:
https://app.snyk.io/org/sammyfilly/project/a212166a-dd80-4d05-bc70-626f4e241e64?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot

backend/package-lock.json

@@ -44,7 +44,7 @@
     "crypto-js": "~4.1.1",
     "express": "~4.18.2",
     "maxmind": "~4.3.8",
-    "mysql2": "~3.2.0",
+    "mysql2": "~3.9.7",
     "node-worker-threads-pool": "~1.5.1",
     "socks-proxy-agent": "~7.0.0",
     "typescript": "~4.7.4",