Write or modify existing snapshot-test that runs ES-MDA to include outliers

A recent bug in ERT's outlier detection shows the need for adding a test-run that has outliers.

Start by locating the existing snapshot test or test-run that exercises ES-MDA, then trace how outlier detection is configured in that test setup. Add coverage for a run containing outliers and confirm the snapshot or test result captures the expected behavior described in the issue.

Written by the indexing model from the issue text.