remove_installed!

# File lib/rubygems/available_set.rb, line 149
  def remove_installed!(dep)
    @set.reject! do |t|
      # already locally installed
      Gem::Specification.any? do |installed_spec|
        dep.name == installed_spec.name and
          dep.requirement.satisfied_by? installed_spec.version
      end
    end

    @sorted = nil
    self
  end