Update build GHA Workflow for Newer coveralls-python Configurations

[mcdonnnj]

💡 Summary

@dav3r ran into and fixed an issue with the coveralls-python configuration in cisagov/gophish-tools#29 and based on the configuration documentation for coveralls-python it appears that we need to update build.yml to reflect these adjustments.

Motivation and context

Fix an apparent bug and fully support the parallelization we already use.

Implementation notes

Please provide details for implementation, such as:

• Update to use GITHUB_TOKEN instead of COVERALLS_REPO_TOKEN
• Update to support the parallelization we use to test all supported Python versions.

Acceptance criteria

• Actions run successfully using the new secret value.
• Parallel jobs are correctly flagged to help checking possible changes between Python versions.

[dav3r]

@mcdonnnj Thanks for putting in this issue! 👍