Add documentation on how to remove blobs from the repository

What does this MR do and why?

Adds documentation on how to remove blobs from the repository + updates related links.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

No visual changes are expected

How to set up and validate locally

1. Enable the rewrite_history_ui feature flag.
2. Navigate to Project > Setting > Repository > Repository maintenance
3. Click on the link labeled How do I get a list of object IDs?

Related to #464252, https://gitlab.com/gitlab-org/gitlab/-/issues/450701