When a contributor was removed from `contributors.json`, the
corresponding image should also be removed from
`aio/content/images/bios/`. However, this was often overlooked,
resulting in unused images remaining in `aio/content/images/bios/`.
This commit adds a check to ensure that all images in
`aio/content/images/bios/` are referenced in `contributors.json`.
PR Close#41290