Question: when did iron brew change to irn bru
[{'answer': 'July 1946', 'provenance': [{'wikipedia_id': '14741', 'title': 'Irn-Bru', 'start_paragraph_id': 6, 'start_character': 67, 'end_paragraph_id': 6, 'end_character': 76, 'bleu_score': 1.0, 'section': 'Section::::Overview.:Early history.\n'}]}, {'provenance': [{'wikipedia_id': '14741', 'title': 'Irn-Bru', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 1020, 'bleu_score': 0.9670935813421611, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10896475719489371276}, 'section': 'Section::::Overview.:Early history.\n'}]}]