Using wostringstream only on Windows (#21938)
### Description
Using wostringstream only on Windows
### Motivation and Context
From line
[62](https://github.com/microsoft/onnxruntime/pull/21938/files#diff-47776d020ac08134de4059eab473550237f4999c598ab56afad3676d2f193edcR62),
currently, `stream_` can be either `wostringstream` or `ostringstream`
depending on the OS, however, for Unix like system, `stream_` should be
`ostringstream`, instead of.
