Revert "Revert "Revert "Pin version of setuptools"""

This reverts commit 2191f838a718049b3ba3be42f3aef8a970ff4278.

Approve once Setuptools 8 is silencing runtime warnings by default,
e.g. via https://github.com/jaraco/setuptools/pull/23 or a similar
patch.

Change-Id: I3c97a4d7810870c9ac058350b362930ce2af713b
Merge "Revert "Revert "Revert "Pin version of setuptools""""
Merge branch 'master' of https://github.com/openstack-dev/devstack