Add conflict so that Drush users know to also upgrade it.

composer.json

@@ -21,7 +21,8 @@
     "kint-php/kint": "Kint provides an informative display of arrays/objects. Useful for debugging and developing."
   },
   "conflict": {
-    "kint-php/kint": "<3"
+    "kint-php/kint": "<3",
+    "drush/drush": "<12.5.1"
   },
   "config": {
     "allow-plugins": {