Verification: Add missing id for form label to work

What does this MR do and why?

Verification: Add missing id for form label to work

Adds missing id to form input

See also working example: https://gitlab.com/gitlab-org/gitlab/-/blob/df9af7b4565c2a2095300faa14b370b28e465aa1/app/assets/javascripts/sessions/new/components/email_verification.vue

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

How to set up and validate locally

1. Enable Verification settings (see https://docs.gitlab.com/ee/security/identity_verification.html)
2. Verify id is present

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/511805