Unit test job on Windows 10/11 isn't scheduled in Buildkite

This is true of all recent CI runs. See https://buildkite.com/elastic/elastic-agent/builds/36612/steps/canvas?sid=019d4b7f-966b-41c5-afa9-c3f8367857f0&tab=timeline for example.

We should disable it until the infrastructure problem is resolved. Realistically, none of our functionality depends on differences between Windows 10 and 11, so the likelihood of introducing a defect is minimal.

This issue will also track re-enabling the tests.