Fix CI checks: Pin setuptools to <81 for test environments and fix doclink checks

Without an explicit build-system declaration, pip's legacy behavior does not guarantee setuptools is present in the virtualenv.
Python 3.12+ dropped setuptools from the default venv, leaving pkg_resources unavailable at runtime. Stevedore uses pkg_resources
to discover jjb.cli.subcommands entry points, so the CLI fails immediately when it is missing. Pin setuptools to <81 in
both the toml and tox configuration.

Also, remove the anchor reference from the zuul launchers.rst link to resolve check.

Change-Id: Icbde8a7727dc02cce2df7b37a230a18e80c74130

jenkins_jobs/modules/zuul.py

@@ -17,7 +17,7 @@ The Zuul module adds jobs parameters to manually run a build as Zuul would
 have. It is entirely optional, Zuul 2.0+ pass the parameters over Gearman.
 
 .. _expected by Zuul: \
-https://opendev.org/zuul/zuul/src/tag/2.6.0/doc/source/launchers.rst#user-content-zuul-parameters
+https://opendev.org/zuul/zuul/src/tag/2.6.0/doc/source/launchers.rst
 """
 
 import jenkins_jobs.modules.base

pyproject.toml

@@ -0,0 +1,3 @@
+[build-system]
+requires = ["setuptools<81", "pbr>=1.8"]
+build-backend = "setuptools.build_meta"

tox.ini

@@ -13,6 +13,8 @@ setenv =
          VIRTUAL_ENV={envdir}
 usedevelop = True
 install_command = pip install {opts} {packages}
+deps =
+    setuptools<81
 # cleanup is needed mostly for dev environmnts and assures that if  dev
 # is switching branch, no lefovers will impact execution.
 # No git commands here because test should run even from a source archive.