add missing build dependency for onnxruntime_providers_webgpu (#23324)
### Description
Fixes build when specify with flag `--target
onnxruntime_providers_webgpu`
Otherwise the following error will occur:
```
range.cc
D:\code\onnxruntime\build\Windows\Debug\_deps\onnx-src\onnx\onnx_pb.h(65,10): error C1083: Cannot open include file: 'o
nnx/onnx-ml.pb.h': No such file or directory [D:\code\onnxruntime\build\Windows\Debug\onnxruntime_providers_webgpu.vcxp
roj]
(compiling source file '../../../onnxruntime/core/providers/webgpu/math/binary_elementwise_ops.cc')
```