Coder.clean removes `tainted?` flag

[svenfuchs]

irb(main):001:0> require 'coder'
=> true
irb(main):002:0> string = 'a'
=> "a"
irb(main):003:0> string.taint
=> "a"
irb(main):004:0> string.tainted?
=> true
irb(main):005:0> Coder.clean(string).tainted?
=> false