Remove deprecated 'sidebar_current'
Remove deprecated 'sidebar_current'

https://github.com/terraform-providers/terraform-provider-aws/pull/10676/checks?check_run_id=842278427

* bflad/tfproviderdocs#23
* https://github.com/hashicorp/terraform-website#yaml-frontmatter

> sidebar_current (deprecated) — No longer used for anything.
> Omit this from new pages, and feel free to remove it from existing ones.

By @suzuki-shunsuke

terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws