Simplify haveWheel condition in setup.py

[echoix]

Following #2687, where the wheel dependency has been changed to use the setuptools recommended approach, as the old pattern would have been removed in October 2025, this PR removes the haveWheel condition from the setup.py. (Unindent code where needed)

In the same depreciation issue handling, the wheel dependency (that was installed through pip), was needed before setuptools 70.1 as it provided the bdist_wheel implementation. Since we already require that minimum setuptools, drop the wheel dependency.

Historical note

This project used to contain the implementation of the setuptools bdist_wheel command, but as of setuptools v70.1, it no longer needs wheel installed for that to work. Thus, you should install this only if you intend to use the wheel command line tool!

From https://pypi.org/project/wheel/

Note that pip wheel doesn't require our project to install wheel to work as before.