Reorder split names

Reorder split names in the YAML metadata to be aligned with the order in the loading script.
See: https://github.com/huggingface/datasets/issues/5258

README.md

@@ -42,15 +42,15 @@ dataset_info:
     dtype: int32
   config_name: plain_text
   splits:
-  - name: test
-    num_bytes: 7167203
-    num_examples: 1894
   - name: train
     num_bytes: 66099232
     num_examples: 15931
   - name: validation
     num_bytes: 8904329
     num_examples: 1991
+  - name: test
+    num_bytes: 7167203
+    num_examples: 1894
   download_size: 7085941
   dataset_size: 82170764
 ---