fix: Fix issue with open router credential test

[Joffcom]

Summary

This PR updates the credential test URL as we were previously using the /models endpoint which doesn't require auth.

Related Linear tickets, Github issues, and Community forum posts

https://linear.app/n8n/issue/AI-838/openrouter-cred-test-fix closes #14432

Review / Merge checklist

• [x] PR title and summary are descriptive. (conventions)
• [ ] Docs updated or follow-up ticket created.
• [ ] Tests included.
• [ ] PR Labeled with release/backport (if the PR is an urgent fix that needs to be backported)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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[ggozad]

Looks great!

[github-actions[bot]]

:warning: Some Cypress E2E specs are failing, please fix them before merging

[github-actions[bot]]

:warning: Some Cypress E2E specs are failing, please fix them before merging

[github-actions[bot]]

:warning: Some Cypress E2E specs are failing, please fix them before merging

[github-actions[bot]]

:white_check_mark: All Cypress E2E specs passed

[github-actions[bot]]

:warning: Some Cypress E2E specs are failing, please fix them before merging

[github-actions[bot]]

:warning: Some Cypress E2E specs are failing, please fix them before merging

[github-actions[bot]]

:warning: Some Cypress E2E specs are failing, please fix them before merging

[github-actions[bot]]

:warning: Some Cypress E2E specs are failing, please fix them before merging

[github-actions[bot]]

:white_check_mark: All Cypress E2E specs passed

[janober]

Got released with [email protected]