message: remove empty CtcLossDescriptor in dnn.h
diff: @@ -190,13 +190,6 @@ class RnnDescriptor {
  virtual ParamsRegions ParamsBiasRegions() const { return ParamsRegions(); }
  };
  -// Describes a CTC loss operation.
  -class CtcLossDescriptor {
  - public:
  - CtcLossDescriptor() {}
  - ~CtcLossDescriptor() {}
  -};
  -
  // Specifies the sequence in a RNN model.
  //
  // The user is responsible for releasing this descriptor when it is no longer
  