KNOX-3394: Correct outdated unittest documentation in Docker Compose …

[Raghav-Mah3shwari]

What changes were proposed in this pull request?

This PR updates .github/workflows/tests/README.md so contributor documentation matches how Docker Compose integration tests actually run in CI and locally.

Changes include:

• Document pytest as the test runner instead of unittest
• Replace the unittest-based example with pytest-style test functions and assert statements
• Note that existing unittest.TestCase tests remain supported by pytest
• Update subdirectory discovery guidance for pytest (recursive discovery; __init__.py optional)
• Correct the "How It Works" section to describe the real CI behavior: pytest with single-EKU suites excluded and run separately by the workflow

No test code or workflow behavior is changed—documentation only.

How was this patch tested?

Documentation-only change; no runtime behavior was modified.

Verification:

1. Reviewed .github/workflows/compose/docker-compose.yml and confirmed the tests service runs pytest (not python -m unittest discover)
2. Reviewed .github/workflows/tests.yml and confirmed single-EKU suites are run in separate workflow steps
3. Compared README examples against existing tests in .github/workflows/tests/ (e.g. unittest.TestCase classes still valid under pytest)
4. Manually proofread the updated README for accuracy and consistency

Integration Tests

No new or updated integration tests are required. This change only updates contributor documentation; it does not modify test logic, Compose configuration, or CI workflows.

UI changes

N/A — documentation-only change.

[github-actions]

Test Results

40 tests   40 ✅  5s ⏱️
 3 suites   0 💤
 3 files     0 ❌

Results for commit a7ad17f.