Try to fix build failure on ubuntu & mac.

Author: Masaru Kimura

src/Native/LibTorchSharp/THSJIT.cpp

@@ -74,7 +74,7 @@ void THSJIT_Module_zero_grad(const JITModule module, bool set_to_none)
     // torch::jit::Module has no zero_grad().
     // As a workaround, manually loop over the parameters and zero them out like optimizer does;
     // https://github.com/pytorch/pytorch/blob/v2.5.1/torch/csrc/api/src/optim/optimizer.cpp#L123
-    for (auto& p : (*module)->parameters()) {
+    for (const auto& p : (*module)->parameters()) {
         if (p.mutable_grad().defined()) {
             p.mutable_grad().detach_();
             if (set_to_none)