Convert archive_rate_limit feature flag to Application Setting
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### Context
There are two issues to solve:
1. `archive_rate_limit` is meant to be a temporary feature flag. It's enabled in Gitlab.com.
2. There is no way to configure the `project_repositories_archive` rate - [it's currently hard-coded](https://gitlab.com/gitlab-org/gitlab/blob/a801d252814233364563f2cda64bd6a83b0f3c2c/lib/gitlab/application_rate_limiter.rb#L74-74) to `5` per `1.minute`.
### Requirements
Remove the `archive_rate_limit` feature flag in favor of an application setting for `project_repositories_archive`.
### Implementation plan
Follow [this guideline](https://docs.gitlab.com/development/application_settings/#add-a-new-application-setting) to add the new application setting. There are a list of steps that you should follow.
issue