Fix `license` metadata

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

Thanks! 🙏

README.md

@@ -5,7 +5,7 @@ annotations_creators:
 - machine-generated
 language_creators:
 - found
-languages:
+language:
   ecthr:
   - en
   scotus:
@@ -16,7 +16,7 @@ languages:
   - it
   cail:
   - zh
-licenses:
+license:
 - cc-by-nc-sa-4.0
 multilinguality:
   ecthr: