Question: who has won the most uefa champions league cups
[{'answer': '21'}, {'provenance': [{'wikipedia_id': '19012416', 'title': 'List of UEFA club competition winners', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 496, 'bleu_score': 0.9183330560237911, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3782655062390875693}, 'section': 'Section::::Abstract.'}]}]