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

@@ -172,12 +172,12 @@ dataset_info:
     dtype: int32
   config_name: plain_text
   splits:
-  - name: test
-    num_bytes: 745260
-    num_examples: 180
   - name: train
     num_bytes: 10762355
     num_examples: 1448
+  - name: test
+    num_bytes: 745260
+    num_examples: 180
   - name: validation
     num_bytes: 1646596
     num_examples: 200