Sass deprecation message on install

[clgroft]

Running bundle install on a fresh repo, I saw the following:

Post-install message from sass:

Ruby Sass is deprecated and will be unmaintained as of 26 March 2019.

* If you use Sass as a command-line tool, we recommend using Dart Sass, the new
  primary implementation: https://sass-lang.com/install

* If you use Sass as a plug-in for a Ruby web framework, we recommend using the
  sassc gem: https://github.com/sass/sassc-ruby#readme

* For more details, please refer to the Sass blog:
  http://sass.logdown.com/posts/7081811

Looking at rails/sass-rails#420, it seems that version 6.0 of the sass-rails gem will be a wrapper for sassc-rails. We could wait for the new version or switch to sassc-rails now. I don't have enough context yet to know which makes more sense.

[clgroft]

Alternately, since there aren't any SCSS files in the project, we might not even need sass-rails.

[sdspikes]

yeah, this is what I get for doing rails new and not bothering to configure it much -- lots of stuff we don't need. Probably safe to remove.