Support next-gen Docker convenience images

[jrgriffiniii]

While this is currently supported within this source code base, I am finding the following on the Orb Registry:

https://circleci.com/developer/orbs/orb/samvera/circleci-orb#executors-ruby

This should be cimg/, as is found within https://github.com/samvera-labs/samvera-circleci-orb/blob/main/src/executors/ruby.yml#L10

[jrgriffiniii]

This was created in error, as this is was in place, https://github.com/samvera/samvera-circleci-orb/blob/main/src/executors/ruby_fcrepo_solr_redis_postgres.yml#L2, but simply not included as a new release for the Orb.