Move @ryanmoran into an Emeritus Maintainer position

[sophiewigmore]

I would like to propose we move @ryanmoran into an Emeritus Maintainer position for the Ruby subteam. He is moving away from the project after a number of years building up the technology and community. Thank you for everything you've done for the project, Ryan!

@paketo-buildpacks/ruby please vote as to whether we should officially make this change
cc @paketo-buildpacks/steering-committee