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

@@ -14,12 +14,12 @@ dataset_info:
   - name: id_string
     dtype: string
   splits:
-  - name: test
-    num_bytes: 1017354
-    num_examples: 1000
   - name: train
     num_bytes: 4711114
     num_examples: 4638
+  - name: test
+    num_bytes: 1017354
+    num_examples: 1000
   - name: validation
     num_bytes: 518604
     num_examples: 500