Update NST.py

NST.py

@@ -259,7 +259,7 @@ class Nst(datasets.GeneratorBasedBuilder):
                             fields["channels"] = 1
                             fields["file"] = fields["file"].replace(".wav", ".mp3")
                             # Fixing some errors in the metadata
-                            if fields["age"] == "slethei":
+                            if fields["age"].lower() == "slethei":
                                 fields["age"] = 0
                             yield metadata_key, {
                                 "id": metadata_key,