MR approval placeholders same size as images

What does this MR do?

Fix Approvers layout bug remove some unused styles (e.g. > span where span had changed)

Are there points in the code the reviewer needs to double check?

• Are the circles correct size? They are bigger than the "available approvers" ones above, and smaller than the Pipeline status icons. That's a lot of different sized circles
• I moved SVG placeholder stuff into link_to_member_avatar.js (see screenshots). Seemed to be passing a lot of props for no reason, unless there are other SVGs used for that image.

Why was this MR needed?

regression

Screenshots (if relevant)

Default image placeholder behaviour

Old - broken image was squircle:

New, broken image is placeholder:

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [ ] Documentation created/updated
• [ ] API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #2491 (closed)