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

@@ -39,12 +39,12 @@ dataset_info:
   - name: highlights
     dtype: string
   splits:
-  - name: test
-    num_bytes: 25693509
-    num_examples: 5638
   - name: train
     num_bytes: 207186608
     num_examples: 45654
+  - name: test
+    num_bytes: 25693509
+    num_examples: 5638
   - name: validation
     num_bytes: 23130954
     num_examples: 5074