Removes design docs from 21 and 22 w/o cells and adds redirects

What does this MR do?

❗ Adds remaining design documents from 2021 and 2022 (gitlab-com/content-sites/handbook!7003 - merged) is a MR dependency for this MR ❗ We should only merge this once the dependency has been deployed!

We are currently migrating the Architecture design documents from the gitlab project to the public handbook.

gitlab-com/content-sites/handbook!7003 (merged) adds all design documents from 2021 and 2022 (except cells) to the handbook. Now this MR removes the original documents from the gitlab repository and instead adds redirects to the handbook.

Excerpt from design docs table. These documents are in this MR.

Design document folder	Creation Date	Migrated?	Redirect?
graphql_api	2021-01-07	👷
ci_scale	2021-01-21	👷
consolidating_groups_and_projects	2021-02-07	👷
ci_data_decay	2021-09-10	👷
object_storage	2021-11-18	👷
runner_scaling	2022-01-19	👷
rate_limiting	2022-09-08	👷
work_items	2022-09-28	👷
runner_tokens	2022-10-27	👷
observability_metrics	2022-11-09	👷
remote_development	2022-11-15	👷
secret_detection	2022-11-25	👷
code_search_with_zoekt	2022-12-28	👷 until here gitlab-com/content-sites/handbook!7003 (merged)

Technical Writing maintainer review

Once approved, please ask @phillipwells for the Technical Writing review, so we can merge this. Additionally, post this or a similar message to the #docs Slack channel for visibility and if someone else wants to jump in:

Hello everyone :wave: this is another removal and redirect MR for
the architecture design documents migration. [LINK TO MR]

Phillipp Wells can you or someone else from your team please review
and merge this? :bow: Thanks a lot in advance :slight_smile:

Migration issue: https://gitlab.com/gitlab-com/content-sites/handbook/-/issues/279

Related issues

gitlab-com/content-sites/handbook#279 (closed)

Author's checklist

• Optional. Consider taking the GitLab Technical Writing Fundamentals course.
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If you are a GitLab team member and only adding documentation, do not add any of the following labels:

• ~"frontend"
• ~"backend"
• ~"type::bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

Reviewer's checklist

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If you aren't sure which tech writer to ask, use roulette or ask in the #docs Slack channel.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
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    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
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