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

@@ -35,12 +35,12 @@ dataset_info:
           5: afya
   config_name: swahili_news
   splits:
-  - name: test
-    num_bytes: 16093496
-    num_examples: 7338
   - name: train
     num_bytes: 49517855
     num_examples: 22207
+  - name: test
+    num_bytes: 16093496
+    num_examples: 7338
   download_size: 65618408
   dataset_size: 65611351
 ---