AP-806 - Update using-integration-for-testing.html.md.erb

[ImogenCraigmile]

https://govukverify.atlassian.net/browse/AP-806

Why

It isn't necessary to have the test user data to test an authentication only journey, the existing documentation is causing users who do not need the test users to ask for the document. This is creating unnecessary work for the onboarding team to respond so the docs needs changing to accommodate this.

What

Added a line to explain that you don't need the user data for an auth only journey and removed references to it.

Technical writer support

Do you need a tech writer's support, for example to review your PR? Yes please.

How to review

• /preview-with-docker.sh
• http://localhost:4567/test-your-integration/using-integration-for-testing/

Changelog

If this change is significant (for example, launching a new feature or deprecating a feature), you should update the changelog found at partials/_changelog.erb under the heading 'Documentation updates'.

Confirm

• I have checked if any docs change here also requires updates to other repositories (ADRs / RFCs, README.md, Team Manual, elsewhere in these docs)
• Where there is any overlap I have updated or opened a PR for corresponding changes