fix mysql2 version to 3.2.0 for node 14 support

package.json

@@ -32,7 +32,7 @@
   },
   "dependencies": {
     "debug": "^4.3.4",
-    "mysql2": "3.2.0", // lru-cache < 8 @ node 14
+    "mysql2": "3.2.0",
     "node-cache": "^5.1.2"
   }
 }