Remove Danger warnings for changes in tests

What does this MR do and why?

This change removes data-testid warnings when only tests have changed. It preserves warnings when production code has changed.

As our tests are the ones validating the test ids, a change that only impacts tests wouldn't change the outcome of other higher tests: e.g. a refactor in our unit tests don't require review or re-run of e2e tests.

Screenshots or screen recordings

For example, we don't want this warning to be triggered by changes in the tests themselves:

How to set up and validate locally

I added a mock commit with testid changes in both specs and production code and ran:

bundle exec rake danger_local

Only production code is shown.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.