Added support for Google Ads API v24_1.

• Add support for v24 of the Google Ads API.
• Removed support for Google Ads API v23.
• Updated code examples: generate_forecast_metrics, add_performance_max_campaign.

Add support for v23_2 of the Google Ads API.

• Added support for Google Ads API v23_1.
• Added support for Google Ads API v20_2, v21_1, and v22_1, which contain
  EU political advertising-related changes.
• Added code examples: fetch_incentives, apply_incentive.

• Added support for Google Ads API v23.
• Removed support for Google Ads API v19.
• Renamed campaign start_date and end_date fields to start_date_time and
  end_date_time.
• Removed add_call_add example.

• Added support for Google Ads API v22.
• Fixed a typo in the BudgetPerDayMinimumErrorDetails.minimum_budget_amount_micros
  field.
• Updated PMax-related examples to remove the use of urlExpansionOptOut.

• Added support for Google Ads API v21.
• Added support for Google Ads API v19_2 and v20_1, which contain EU
  political advertising-related changes.
• Removed support for Google Ads API v18.
• Added code example: add_demand_gen_campaign.
• Updated campaign-related examples to set the containsEuPoliticalAdvertising
  field.

Fixed bug in v20 CampaignBudget resource.

• Added support for Google Ads API v20.
• Removed support for Google Ads API v17.

• Added support for Google Ads API v19_1.
• Updated upload_enhanced_conversions_for_leads example to use session attributes.