Remove the AWS S3 upload steps from the release workflow, keeping Cloudflare R2 as the only object storage target.
- Drop the `aws credential configure` step and the AWS-specific secrets usage.
- Drop the `copy files to S3 and clear cache` step.
- The awscli install is kept because the Cloudflare R2 sync still relies on it.
Reviewed-on: https://gitea.com/gitea/helm-actions/pulls/178
Reviewed-by: DaanSelen <135789+daanselen@noreply.gitea.com>