fix: update prompt_template to <image>{{ question }}\n

metadata.json

@@ -10,7 +10,7 @@
         "image"
       ],
       "task_type": "vqa",
-      "prompt_template": "{{ question }}\n",
+      "prompt_template": "<image>{{ question }}\n",
       "mapping_from_source": {
         "media": {
           "from": "image",