Refine prompt_template_source: lmms-eval/VLMEvalKit canonical citations

metadata.json

@@ -50,8 +50,9 @@
         }
       },
       "prompt_template_source": {
-        "origin": "fallback",
-        "reference": "T2"
+        "origin": "official",
+        "reference": "https://github.com/EvolvingLMMs-Lab/lmms-eval/blob/main/lmms_eval/tasks/visualmrc/utils.py (visualmrc_doc_to_text — bare question; reading comprehension)",
+        "notes": "lmms-eval VisualMRC canonical evaluation prompt."
       }
     }
   }