renovate: disable devbox package manager

This disables recently added renovate package manager. We generally
don't want to have this automatically updated because whole point of
creating an isolated dev environment is to have the ability to pin
specific versions of the dependencies without affecting anyone else.

Author: skrobul

.github/renovate.json

@@ -25,5 +25,8 @@
       ],
       "datasourceTemplate": "helm"
     }
-  ]
+  ],
+  "devbox": {
+    "enabled": false
+  }
 }