Docs: Remove all remaining orphaned images.

What does this MR do?

This MR deletes all "orphaned" images, which are images that used to be used in docs, but are no longer linked to by any doc. This is usually due to:

• a doc being deleted, but not the images it used.
• a doc being moved, and the images were copied to a new location (but not deleted from the original location).
• a new image uploaded using a new name, and the previous image removed from the markdown in the doc (but not deleted).
• many images being uploaded with a new doc, but some images not used in the final version.

Since this commit passes the link check lint, I'm confident that there are no docs linking to these images, and therefore they are no longer in use and can be deleted.

Related issues

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/61947

Author's checklist

• Follow the Documentation Guidelines and Style Guide.
• Link docs to and from the higher-level index page, plus other related docs where helpful.
• Apply the ~Documentation label.

Review checklist

All reviewers can help ensure accuracy, clarity, completeness, and adherence to the Documentation Guidelines and Style Guide.

1. Primary Reviewer

• Review by a code reviewer or other selected colleague to confirm accuracy, clarity, and completeness. This can be skipped for minor fixes without substantive content changes.

2. Technical Writer

• Optional: Technical writer review. If not requested for this MR, must be scheduled post-merge. To request for this MR, assign the writer listed for the applicable DevOps stage.

3. Maintainer

1. Review by assigned maintainer, who can always request/require the above reviews. Maintainer's review can occur before or after a technical writer review.
2. Ensure a release milestone is set and that you merge the equivalent EE MR before the CE MR if both exist.
3. If there has not been a technical writer review, create an issue for one using the Doc Review template.