Freeing character level WMTProblems from needing a targeted_vocab_size.
Freeing character level WMTProblems from needing a targeted_vocab_size.

PiperOrigin-RevId: 163846429

tensorflow/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,vthorsteinsson/tensor2tensor,rsepassi/tensor2tensor,rsepassi/tensor2tensor,waterblue13/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,rsepassi/tensor2tensor,rsepassi/tensor2tensor,waterblue13/tensor2tensor,vthorsteinsson/tensor2tensor,waterblue13/tensor2tensor,tensorflow/tensor2tensor,tensorflow/tensor2tensor