scale reCAPTCHA to be full width of the register form

What does this MR do?

add margin bottom to

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

• maybe there is a better way?

Why was this MR needed?

• switching to Invisible recaptcha was a bit much scope for now

Screenshots (if relevant)

320px screen:

600px screen

900px screen

1000px screen

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 #29000 (closed)