When I made changes to our configforms CSS to use Ink for more things, I mistakenly changed several of our LESS variable definitions to use the new CSS variables. This works for many things, but crashes if another file tries to use LESS operators (such as `darken()` or simple calculations) with them. This change reverts the old LESS variables back to their old values, and then updates the rules to reference our ink variables directly. Testing Done: - Grepped around to make sure we weren't using old variables inappropriately (there will be a couple fixes elsewhere) - Verified the appearance of configforms pages in Review Board's "My Account" and admin integrations list pages.