bug#74739: 31.0.50; eshell/which doesn't return a non-zero exit code on not finding a file

[Jim Porter]

On 12/8/2024 8:30 AM, the_wurfkreuz via Bug reports for GNU Emacs, the 
Swiss army knife of text editors wrote:
> eshell/which doesn't return a non-zero exit code on not finding a file. 
> Yet it sends the output to stderr. It looks like there is an inconsistency.

Thanks for noticing this. Fixed in b6c91cdf541. Closing this bug now.