Fix margin for submit button with captcha

What does this MR do and why?

Fixes the spacing between captcha and submit button on trial registration login

Screenshots or screen recordings

instance	before	after
.com
any other instance
no captcha	-

How to set up and validate locally(if you want more than the screenshots)

1. sign out
2. setup a domain on ngrok
3. start ngrok server locally forwarding the port to your gdk in terminal.
   • example: ngrok http --region=us --hostname=douggdk.ngrok.io 3000
4. add your ngrok domain to allowed_hosts: ['douggdk.ngrok.io'] in your config/gitlab.yml
5. restart gdk
6. setup recaptcha - https://docs.gitlab.com/ee/integration/recaptcha.html#configuration
7. visit http://gdk.test:3000/-/trial_registrations/new?glm_source=about.gitlab.com&glm_content=free-trial on your local gdk.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.