🚨 Update to heroku-22 stack by 2023-04-30 🚨

[coltborg]

Our current heroku-18 stack is being deprecated April 30th, 2023. In order to upgrade to heroku-22, we'll need to upgrade our .ruby-version.

 !     The Ruby version you are trying to install does not exist on this stack.
 !     
 !     You are trying to install ruby-2.5.3 on heroku-22.
 !     
 !     Ruby ruby-2.5.3 is present on the following stacks:
 !     
 !     - heroku-18
 !     
 !     Heroku recommends you use the latest supported Ruby version listed here:
 !     https://devcenter.heroku.com/articles/ruby-support#supported-runtimes
 !     
 !     For more information on syntax for declaring a Ruby version see:
 !     https://devcenter.heroku.com/articles/ruby-versions

[coltborg]

Done