Failing macOS tests

[davidmfinol]

Bug description

macOS tests are failing in runs such as https://github.com/game-ci/unity-builder/actions/runs/11224782350/workflow

How to reproduce

Trigger https://github.com/game-ci/unity-builder/blob/main/.github/workflows/build-tests-mac.yml

Expected behavior

All tests should pass

Additional details

Creating this issue for tracking purposes

[davidmfinol]

Failing tests seem to be related to v2021, which is reaching EOL.
We should replace those tests with test for Unity 6.
Related issue: game-ci/docker#220