docs: update sample for query_to_arrow to use query_and_wait API (#1776)

Co-authored-by: Salem Boyland <salemb@google.com>
Co-authored-by: Kira <kirnendra@google.com>
Co-authored-by: Chalmer Lowe <chalmerlowe@google.com>

samples/query_to_arrow.py

@@ -44,8 +44,8 @@ def query_to_arrow() -> "pyarrow.Table":
     FROM races r
     CROSS JOIN UNNEST(r.participants) as participant;
     """
-    query_job = client.query(sql)
-    arrow_table = query_job.to_arrow()  # Make an API request.
+    results = client.query_and_wait(sql)
+    arrow_table = results.to_arrow()  # Make an API request.
 
     print(
         "Downloaded {} rows, {} columns.".format(