Fix typos: GCP_BUCKET should be GCS_BUCKET

Author: ageron

docs/beam_datasets.md

@@ -71,7 +71,7 @@ python -m tensorflow_datasets.scripts.download_and_prepare \
   --data_dir=$GCP_BUCKET/tensorflow_datasets \
   --beam_pipeline_options=\
 "runner=DataflowRunner,project=$GCP_PROJECT,job_name=$DATASET_NAME-gen,"\
-"staging_location=$GCP_BUCKET/binaries,temp_location=$GCP_BUCKET/temp,"\
+"staging_location=$GCS_BUCKET/binaries,temp_location=$GCS_BUCKET/temp,"\
 "requirements_file=/tmp/beam_requirements.txt"
 ```