Set task_type to CAUSAL_LM so the Hub parses the adapter config

adapter_config.json

@@ -49,11 +49,11 @@
     "in_proj_qkv"
   ],
   "target_parameters": null,
-  "task_type": null,
+  "task_type": "CAUSAL_LM",
   "trainable_token_indices": null,
   "use_bdlora": null,
   "use_dora": false,
   "use_qalora": false,
   "use_rslora": false,
   "velora_config": null
-}
+}