Log Message:
gitea: Update to 1.18.0.

The list of changes since 1.16.9 is nearly 600 lines long, so please
see the following URLs for a curated list of changes:

  https://blog.gitea.io/2022/12/gitea-1.18.0-is-released/
  https://blog.gitea.io/2022/12/gitea-1.17.4-is-released/
  https://blog.gitea.io/2022/10/gitea-1.17.3-is-released/
  https://blog.gitea.io/2022/09/gitea-1.17.2-is-released/
  https://blog.gitea.io/2022/08/gitea-1.17.1-is-released/
  https://blog.gitea.io/2022/07/gitea-1.17.0-is-released/