updated field names from 'ner_tags' to 'tags'

conll2012.py

@@ -132,7 +132,7 @@ class Conll2012(datasets.GeneratorBasedBuilder):
                             ]
                         )
                     ),
-                    "ner_tags": datasets.Sequence(
+                    "tags": datasets.Sequence(
                         datasets.features.ClassLabel(
                             names=[
                                 'O',