bug#81517: 31.0.90; executable-find on remote buffer fails

Thanks for quickly response.

 > It has been fixed with bug#81280. The fix is in master, not in the
 > emacs-31 branch. It covers also call-process and make-process.

I applied that fix to files.el and found it works fine, without any
degrades also on macOS environment.

If this commit is merged to Emacs31, many Windows users are happy.

Best regards.
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