Reset instance setting after test and fix sleep placement

What does this MR do?

1. Tries to address #247743 (closed) by resetting the require_admin_approval_after_user_signup instance setting after the test.
2. Fixes the sleep misplacement. It should be placed before submitting the form and not after.
3. Retries clicking on get_started_button if the first click fails. This issue mostly happens on local.

Closes #290002 (closed)

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team