Fix to reference the right instance job object (#1599)

Signed-off-by: Jules Damji <dmatrix@comcast.net>

sdk/python/feast/feature_store.py

@@ -279,7 +279,7 @@ def get_historical_features(
             >>>     entity_df="SELECT event_timestamp, order_id, customer_id from gcp_project.my_ds.customer_orders",
             >>>     feature_refs=["customer:age", "customer:avg_orders_1d", "customer:avg_orders_7d"]
             >>> )
-            >>> feature_data = job.to_df()
+            >>> feature_data = retrieval_job.to_df()
             >>> model.fit(feature_data) # insert your modeling framework here.
         """