Drop Relation::Calculation +options+ arguments

Clean up TODOs now that support for AR deprecated_finders have been
removed

Notice this while looking into a change of behaviour on Relation#maximum probably caused by https://github.com/rails/rails/pull/10561, see https://github.com/huoxito/spree/commit/84262b3d3f3739e43fcb48d819d9e93ec309c53f for details, which I believe is fine. CHANGELOG tells me that deprecated_finders support has been removed so I figured removing those TODOs would be fine too hopefully.