wheel.mk & setuptools: py-wheel mostly unneeded nowadays

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

wheel.mk supports multiple Python build systems, but the most common
one is py-setuptools.

So in most cases, one uses

TOOL_DEPENDS+=	  ${PYPKGPREFIX}-setuptools-[0-9]*:../../devel/py-setuptools
...
.include "../../lang/python/wheel.mk"

We also had py-wheel as a tool dependency in pkgsrc in these cases,
because it was needed at the point wheel.mk was introduced.

Recently I found out that this is not needed any longer. I test-built
the packages using both py-setuptools and py-wheel to confirm that
removing py-wheel is fine, and removed the TOOL_DEPENDS on py-wheel in
most places (some packages actually do want to depend on py-wheel, I
left those alone).

So this is a note to avoid adding unnecessary py-wheel dependencies in
the future. They are not needed any longer.

Thanks!
 Thomas