Fix `license` metadata

We recently updated the datasets metadata for consistency with other repo types (models & spaces)

Thanks! 🙏

README.md

@@ -3,7 +3,7 @@ task_categories:
 - conditional-text-generation
 task_ids:
 - summarization
-languages:
+language:
 - am
 - ar
 - az
@@ -49,7 +49,7 @@ languages:
 - yo
 size_categories:
 - 1M<n<10M
-licenses:
+license:
 - cc-by-nc-sa-4.0
 multilinguality:
 - multilingual