Fix task tags in dataset cards (#4830)

Commit from https://github.com/huggingface/datasets/commit/83f695c14507a3a38e9f4d84612cf49e5f50c153

README.md

@@ -17,13 +17,13 @@ task_categories:
 - text2text-generation
 - translation
 - question-answering
+- summarization
 task_ids:
 - abstractive-qa
 - explanation-generation
 - extractive-qa
 - open-domain-qa
 - open-domain-abstractive-qa
-- summarization
 - text-simplification
 pretty_name: WikiSummary
 ---