fix(wren-ui): see an error when editing a relationship in the defined relationships step of onboarding

[fredalai]

Describe the bug

The user can see the This relationship already exists. error when editing a relationship in the Define relationships step of onboarding.

To Reproduce

Steps to reproduce the behavior:

1. Start onboarding flow
2. Use a database with primary and foreign keys (E.g., Pagila database)
3. Complete the connection to the database, select all tables, and successfully enter the Define relationships step page.
4. After seeing the recommended relationships appear on the table, edit a relationship
5. See This relationship already exists. error

Expected behavior

Will not see the error message when editing a relationship in the Define relationships step of onboarding.

UI Screenshots

Will not see the error message when editing a relationship in the Define relationships step of onboarding.

Rule validator works well

Update relationship

[andreashimin]

lgtm