[js/web] only apply max thread number when it's omitted (#7834)
[js/web] only apply max thread number when it's omitted (#7834)


microsoft/onnxruntime,microsoft/onnxruntime,microsoft/onnxruntime,microsoft/onnxruntime,microsoft/onnxruntime,microsoft/onnxruntime,microsoft/onnxruntime,microsoft/onnxruntime,microsoft/onnxruntime,microsoft/onnxruntime,microsoft/onnxruntime,microsoft/onnxruntime