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

@@ -26,12 +26,12 @@ dataset_info:
   - name: content
     dtype: string
   splits:
-  - name: test
-    num_bytes: 189503
-    num_examples: 3850
   - name: train
     num_bytes: 857391
     num_examples: 17500
+  - name: test
+    num_bytes: 189503
+    num_examples: 3850
   - name: validation
     num_bytes: 184110
     num_examples: 3750