`attr` should be removed
I'm digging through some older Ruby versions and discovered that
attr was deprecated in Ruby 1.9. We still are seeing support for it in Ruby 3.0
Unless there are internals that require its existence, is it time to remove this deprecated feature?
If there's agreement, I'm more than happy to fire up the PR myself. (Also happy to be corrected if there's something I'm missing here :) )