Fix or remove html_proof.rb

[kwalrath]

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>'

[parlough]

This was removed in 99fd6c7