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

@@ -35,15 +35,15 @@ dataset_info:
     dtype: string
   config_name: plain_text
   splits:
-  - name: test
-    num_bytes: 1556379
-    num_examples: 2041
   - name: train
     num_bytes: 4775235
     num_examples: 6116
   - name: validation
     num_bytes: 1539272
     num_examples: 2040
+  - name: test
+    num_bytes: 1556379
+    num_examples: 2041
   download_size: 5558190
   dataset_size: 7870886
 ---