Fix number of samples in README.

The number of samples in each split is incorrect in the README. This results in the following error when loading the dataset:
```
datasets.utils.info_utils.NonMatchingSplitsSizesError: [{'expected': SplitInfo(name='test', num_bytes=0, num_examples=2240, shard_lengths=None, dataset_name=None), 'recorded': SplitInfo(name='test', num_bytes=121453460, num_examples=2241, shard_lengths=None, dataset_name='himanis-line')}]
```

README.md

@@ -18,8 +18,8 @@ dataset_info:
   - name: validation
     num_examples: 2367
   - name: test
-    num_examples: 2240
-  dataset_size: 23111
+    num_examples: 2241
+  dataset_size: 23112
 tags:
   - atr
   - ocr