chore: Update gapic-generator-python to v1.8.5 (#65)

* chore: Update gapic-generator-python to v1.8.5

PiperOrigin-RevId: 511892190

Source-Link: googleapis/googleapis@a45d9c0

Source-Link: googleapis/googleapis-gen@1907294
Copy-Tag: eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiMTkwNzI5NGIxZDgzNjVlYTI0ZjhjNWYyZTA1OWE2NDEyNGM0ZWQzYiJ9

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Anthonios Partheniou <partheniou@google.com>

packages/google-cloud-bigquery-data-exchange/google/cloud/bigquery_data_exchange_v1beta1/types/dataexchange.py

@@ -13,6 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
+from __future__ import annotations
+
 from typing import MutableMapping, MutableSequence
 
 from google.protobuf import field_mask_pb2  # type: ignore