Auto merge of #24041 - asajeffrey:mach-iswindows-isfunction, r=jdm

In mach, add arguments to bare uses of is_windows

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Replace bare uses of `is_windows` by `is_windows()` in mach.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes do not require tests because we don't test infra

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