Fix `license` metadata

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

Thanks! 🙏

README.md

@@ -1,7 +1,7 @@
 ---
 annotations_creators: []
 language_creators: []
-languages:
+language:
 - ar
 - bg
 - de
@@ -22,7 +22,7 @@ languages:
 - ur
 - vi
 - zh
-licenses: []
+license: []
 multilinguality:
 - multilingual
 pretty_name: Language Identification dataset