Fix JS error on welcome page

What does this MR do?

I noticed that on /users/sign_up/welcome page, there is a JS error since an element does not get rendered when the user_other_role_details feature flag is not activated.

How to check

• user_other_role_details feature flag must be disabled
• Sign up as a new user
• (Optional) You might need to approve the new user as the root admin in gitlab -> admin -> user -> pending approvals (http://localhost:3000/admin/users?filter=blocked_pending_approval)
• (Optional) Sign in with the new user
• You will be redirected to the welcome page
• Check the console for the JS error

Screenshots (strongly suggested)

	description
	Error that we get
	The "other" field that gets shown when selected

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

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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