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

@@ -56,12 +56,12 @@ dataset_info:
           24: PU
           25: ART
   splits:
-  - name: test
-    num_bytes: 3095292
-    num_examples: 9987
   - name: train
     num_bytes: 12635011
     num_examples: 37948
+  - name: test
+    num_bytes: 3095292
+    num_examples: 9987
   - name: validation
     num_bytes: 671356
     num_examples: 1997