remove torch dialect from legal list (#1192)

Author: Yancey0623

lib/Conversion/TorchToMhlo/TorchToMhlo.cpp

@@ -43,8 +43,7 @@ class ConvertTorchToMhlo : public ConvertTorchToMhloBase<ConvertTorchToMhlo> {
     MLIRContext *context = &getContext();
     ConversionTarget target(*context);
     target.addLegalDialect<chlo::ChloDialect, mhlo::MhloDialect,
-                           tensor::TensorDialect, arith::ArithmeticDialect,
-                           Torch::TorchDialect>();
+                           tensor::TensorDialect, arith::ArithmeticDialect>();
 
     TypeConverter typeConverter;
     typeConverter.addConversion([](Type type) { return type; });