Cleanup plan for outdated content #2170

We've been discussing the need for updates to the Packaging Guide with the new Python Packaging Council (PPC) (xref python/packaging-council#8). There is a lot of outdated content; adding new content or reshuffling things will be easier once the very outdated stuff is removed. This issue is meant to communicate that plan, and discuss some rough criteria for what can be removed without needing more than two pairs of eyes. A proposal:

In general, everything that is (a) out of date by >3 years, or (b) no longer relevant or maintained can be removed. Examples:

• The News page was last updated in 2019: delete
  • done in removal: news #2173
• The Project summaries page contains packaging tools that saw a last commit years ago: remove those entries from the page
• A discussion about easy_install: delete that page
  • done in removal: easy-install (pip-vs-easy-install page) #2172
• The page install_requires vs requirements files is probably also outdated enough to remove - none of that is standardized or recommended, and it predates pyproject.toml introduction (now 10 years ago)

gh-2165 added a new 404 page, so that pages redirect to the front page (without that, the 404 shown was quite uninformative). Of course if there's a specific replacement for removed content, adding a redirect can be the better option.