Revert "Adds a JRuby optimized version of Concurrent::Atom"
Revert "Adds a JRuby optimized version of Concurrent::Atom"

MadBomber/concurrent-ruby,MadBomber/concurrent-ruby,lucasallan/concurrent-ruby,hobodave/concurrent-ruby,lucasallan/concurrent-ruby,hobodave/concurrent-ruby,lucasallan/concurrent-ruby,ferdinandrosario/concurrent-ruby,hobodave/concurrent-ruby,lucasallan/concurrent-ruby,ferdinandrosario/concurrent-ruby,hobodave/concurrent-ruby,ferdinandrosario/concurrent-ruby,MadBomber/concurrent-ruby,lucasallan/concurrent-ruby,ferdinandrosario/concurrent-ruby,MadBomber/concurrent-ruby