fix(deps): update dependency mysql2 to v3.15.0

Author: renovate-bot

server/package-lock.json

@@ -57,7 +57,7 @@
     "gauss-krueger": "1.0.1",
     "joi": "17.13.3",
     "log4js": "6.9.1",
-    "mysql2": "3.14.1",
+    "mysql2": "3.15.0",
     "sequelize": "6.37.7",
     "serialport": "12.0.0",
     "serve-favicon": "2.5.1",