bpo-36797: Prune more legacy distutils documentation (GH-13092)

Removes more legacy distutils documentation, and more clearly
marks what is left as potentially outdated, with references to
setuptools as a replacement.
diff --git a/Doc/distutils/examples.rst b/Doc/distutils/examples.rst
index f81e06b..4ac552c 100644
--- a/Doc/distutils/examples.rst
+++ b/Doc/distutils/examples.rst
@@ -4,6 +4,8 @@
 Examples
 ********
 
+.. include:: ./_setuptools_disclaimer.rst
+
 This chapter provides a number of basic examples to help get started with
 distutils.  Additional information about using distutils can be found in the
 Distutils Cookbook.