- Lower minimum version requirement for dependencies:
  - google-api-core
  - googleapis-common-protos
  - proto-plus
  - protobuf.
- Update unit tests to run with lowest-supported Google-maintained dependencies.
- Update upload_conversion_enhancement example with recommended placeholder names.
- Update place_id field to place_ids in add_performance_max_for_travel_goals_campaign example.
- Add add_things_to_do_ad example.
- Remove examples:
  - generate_forecast_metrics
  - generate_historical_metrics
  - get_campaign_criterion_bid_modifier_simulations