Fix `license` metadata

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

Thanks! 🙏

README.md

@@ -1,12 +1,12 @@
 ---
 annotations_creators:
 - other
-languages:
+language:
 - en
 - ja
 multilinguality:
 - multilingual
-licenses:
+license:
 - cc-by-4.0
 source_datasets:
 - original