Google Ads API Client Library for Java - v6.0.0

• Added support for Google Ads API v4_0.
• Moved documentation. Now hosted at:
  https://developers.google.com/google-ads/api/docs/client-libs/java.
• Added examples demonstrating:
  • Drafts and experiments.
  • Parallel report download.
  • CPC bid simulations.
  • Programmatic library configuration.
  • Keyword policy violation handling.
  • Updating expanded text ads.
• Removed vulnerable dependency on log4j 1.2.16.
• Added support for linked-customer-id header. This is needed for an extremely
  narrow authentication use-case. Any developer who requires this to be set
  will be advised. It is otherwise safe to ignore.