samples: fixed wrong format on GCS input Uri (#4270)

## Description

Current predict sample indicates that it can multiples GCS URI inputs but it should be singular.

## Checklist
- [X] Please **merge** this PR for me once it is approved.

tables/automl/automl_tables_predict.py

@@ -85,7 +85,7 @@ def batch_predict(
     project_id,
     compute_region,
     model_display_name,
-    gcs_input_uris,
+    gcs_input_uri,
     gcs_output_uri,
 ):
     """Make a batch of predictions."""
@@ -94,17 +94,19 @@ def batch_predict(
     # project_id = 'PROJECT_ID_HERE'
     # compute_region = 'COMPUTE_REGION_HERE'
     # model_display_name = 'MODEL_DISPLAY_NAME_HERE'
-    # gcs_input_uris = ['gs://path/to/file.csv]
-    # gcs_output_uri = 'gs://path'
+    # gcs_input_uri = 'gs://YOUR_BUCKET_ID/path_to_your_input_csv'
+    # gcs_output_uri = 'gs://YOUR_BUCKET_ID/path_to_save_results/'
 
     from google.cloud import automl_v1beta1 as automl
 
     client = automl.TablesClient(project=project_id, region=compute_region)
 
     # Query model
-    response = client.batch_predict(gcs_input_uris=gcs_input_uris,
-                                    gcs_output_uri_prefix=gcs_output_uri,
-                                    model_display_name=model_display_name)
+    response = client.batch_predict(
+        gcs_input_uris=gcs_input_uri,
+        gcs_output_uri_prefix=gcs_output_uri,
+        model_display_name=model_display_name,
+    )
     print("Making batch prediction... ")
     response.result()
     print("Batch prediction complete.\n{}".format(response.metadata))