Increase max state variable counts in solhint config

Caused by the surge of state variables due to upgradeability logic

Author: cygnusv

.solhint.json

@@ -2,6 +2,7 @@
   "extends": "keep",
   "plugins": [],
   "rules": {
+    "max-states-count": ["warn", 20],
     "func-visibility": ["error", { "ignoreConstructors": true }],
     "no-inline-assembly": "off"
   }