Fix docs build for RTD

Author: melissawm

docs/guides/data_input_tfds.md

@@ -5,7 +5,7 @@
 bash download_dataset.sh {GCS_PROJECT} {GCS_BUCKET_NAME}
 ```
 2. In `src/MaxText/configs/base.yml` or through command line, set the following parameters:
-```yml
+```yaml
 dataset_type: tfds
 dataset_name: 'c4/en:3.0.1'
 # set eval_interval > 0 to use the specified eval dataset. Otherwise, only metrics on the train set will be calculated.