Remove universal flag from bdist_wheel config

[yukihiko-shinoda]

Remove universal flag from bdist_wheel config since Python 2 is no longer supported in this project.

@see https://packaging.python.org/guides/distributing-packages-using-setuptools/#universal-wheels

I found some commits with intention to end Python 2 support:

• https://github.com/briggySmalls/cookiecutter-pypackage/commit/6c7f1c40559ac9ed043d98406732b1f2c8315137
• https://github.com/briggySmalls/cookiecutter-pypackage/commit/7ab4e43224c148be4d16f951a3d0ec207ba4c4b4

[briggySmalls]

Oh thank you for this! good spot 👍