Fix or remove html_proof.rb #1461
Description
As of April 16, 2019, ./deploy/html_proof.rb fails. It hasn't changed, so I suspect a ruby change. Here's the output (with ./ substituted for my directory path details):
$ ./deploy/html_proof.rb
./deploy/urls/get_all.rb:3:in `require_relative': cannot load such file --
./deploy/urls/old_site_urls (LoadError)
from ./deploy/urls/get_all.rb:3:in `<top (required)>'
from ./deploy/html_proof.rb:7:in `require_relative'
from ./deploy/html_proof.rb:7:in `<main>'