Update README.md

The code breaks because it is trying to assign the new key `original_answer` to `outputs` which is a list. Instead the original answer can be written to the first element of the outputs list.

README.md

@@ -1182,7 +1182,7 @@ triviaqa_map = {}
 def add_missing_data(x, trivia_qa_subset, triviaqa_map):
     i = triviaqa_map[x['id']]
     x['input'] = trivia_qa_subset[i]['question']
-    x['output']['original_answer'] = trivia_qa_subset[i]['answer']['value']
+    x['output'][0]['original_answer'] = trivia_qa_subset[i]['answer']['value']
     return x
     
 for k in ['train', 'validation', 'test']: