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

@@ -36,12 +36,12 @@ dataset_info:
       sequence: int32
   config_name: ast
   splits:
-  - name: test
-    num_bytes: 907514993
-    num_examples: 50000
   - name: train
     num_bytes: 1870790180
     num_examples: 100000
+  - name: test
+    num_bytes: 907514993
+    num_examples: 50000
   download_size: 526642289
   dataset_size: 2778305173
 ---