Remove obsolete setuptools runtime dependency

[mgorny]

The runtime dependency on setuptools was only required for namespace support. Since pkg_resources-style namespaces have been removed in #52 and there are no relevant imports left in the code, remove the unnecessary dependency.

• I signed and returned the Zope Contributor Agreement, and received and accepted an invitation to join a team in the zopefoundation GitHub organization.
• I verified there aren't any other open pull requests for the same change.
• I followed the guidelines in Developer guidelines.
• I successfully ran code quality checks on my changes locally.
• I successfully ran tests on my changes locally.
• If needed, I added new tests for my changes.
• If needed, I added documentation for my changes.
• I included a change log entry in my commits.

[mgorny]

@icemac, I see the same problem applies to other packages released yesterday. Should I open separate PRs for all of them, or could you perhaps handle it en masse?

[icemac]

@mgorny Thank you for the PR. My idea was to solve this issue more generally via zopefoundation/meta#345 – but it can take some time until I'll be able to tackle it. So I'd appreciate individual PRs for the repositories where the setuptools dependency bothers you.

[mgorny]

Thanks, I'll do that when I have some time.

[cjwatson]

@mgorny I've filed a bunch of individual PRs for this, but just for zope.* packages that are in Debian.

[mgorny]

Thanks! I'm sorry for not being able to look at it sooner.

[mgorny]

Okay, I've filed PRs for the two extra packages that we had, and that should cover them all. Thanks again!