Remove unnecessary PYBUILD_NAME variable

I am proposing this MR due to this statement in Kali's docs (https://www.kali.org/docs/development/intro-to-packaging-example/#rules):

We also need to tell it to use pybuild to build, as we have a setup.py file included in the source of the application. If there was not a setup.py file, we would not add this flag. We also need to tell PyBuild the name of the application. This looks like:

Initially, this was an oversight on my end, since there is no setup.cfg and I have been using my "boilerplate" I made for Python packages. Based on my testing, the package is still installed under the same directory, so either keeping or removing this line has no impact on the package, but I am having a bit of a hard time understanding why Debian's documentation (https://wiki.debian.org/Python/LibraryStyleGuide) keeps this line, even when there is no setup.cfg.

And yes, if --buildsystem=pybuild is removed, the package is hollow, I know. It just doesn't make sense to me for a tool/software to use pybuild when the documentation says pybuild is needed for packages with setup.py.