[E2E] Fixes for login after approval spec

What does this MR do and why?

• Adds a valid assertion to the login after approval spec
• Fixes some timing issues with the login after approval spec

How to set up and validate locally

1. bundle exec rspec qa/specs/features/browser_ui/10_govern/login/register_spec.rb NB -- may need to remove quarantine tags from the spec as it doesn't seem to recognise that the quarantine is specific to 1 job
2. bundle exec rspec qa/specs/features/ee/browser_ui/11_fulfillment/purchase/user_registration_billing_spec.rb

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.