Fix `license` metadata

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

Thanks! 🙏

README.md

@@ -1,10 +1,10 @@
 ---
 language_creators:
 - expert-generated
-languages:
+language:
 - ab
 - ru
-licenses:
+license:
 - cc0-1.0
 multilinguality:
 - translation