Replace YAML keys from int to str

Replace YAML metadata integer keys with strings, as the Hub does not support integers.
See: https://github.com/huggingface/datasets/issues/5275

README.md

@@ -1,5 +1,4 @@
 ---
-pretty_name: Turku NER corpus
 annotations_creators:
 - expert-generated
 language_creators:
@@ -18,7 +17,7 @@ task_categories:
 - token-classification
 task_ids:
 - named-entity-recognition
-paperswithcode_id: null
+pretty_name: Turku NER corpus
 dataset_info:
   features:
   - name: id
@@ -29,19 +28,19 @@ dataset_info:
     sequence:
       class_label:
         names:
-          0: B-DATE
-          1: B-EVENT
-          2: B-LOC
-          3: B-ORG
-          4: B-PER
-          5: B-PRO
-          6: I-DATE
-          7: I-EVENT
-          8: I-LOC
-          9: I-ORG
-          10: I-PER
-          11: I-PRO
-          12: O
+          '0': B-DATE
+          '1': B-EVENT
+          '2': B-LOC
+          '3': B-ORG
+          '4': B-PER
+          '5': B-PRO
+          '6': I-DATE
+          '7': I-EVENT
+          '8': I-LOC
+          '9': I-ORG
+          '10': I-PER
+          '11': I-PRO
+          '12': O
   splits:
   - name: train
     num_bytes: 3257447