Fix `license` metadata

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

Thanks! 🙏

README.md

@@ -2,9 +2,9 @@
 annotations_creators: []
 language_creators:
 - crowdsourced
-languages:
+language:
 - en-US
-licenses: []
+license: []
 multilinguality:
 - monolingual
 pretty_name: github-issues