Update README.md

Added information about train_quality to the splits metadata fixing an unexpected splits exception.

README.md

@@ -126,6 +126,9 @@ dataset_info:
           '0': 'No'
           '1': 'Yes'
   splits:
+  - name: train_quality
+    num_bytes: 344101633249.375
+    num_examples: 1196221
   - name: validation
     num_bytes: 5296900547.25
     num_examples: 18582