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:
           3: S
   config_name: amttl
   splits:
-  - name: test
-    num_bytes: 328525
-    num_examples: 908
   - name: train
     num_bytes: 1132212
     num_examples: 3063
   - name: validation
     num_bytes: 324374
     num_examples: 822
+  - name: test
+    num_bytes: 328525
+    num_examples: 908
   download_size: 685534
   dataset_size: 1785111
 ---