In most scenarios, the client OS is not going to matter. But for your specific question, if you are asking if you patch your Win 10 version to a later patch (e.g. 1909), will this work with 7.3.1? I do not see why not. If you already were on Win 10 using 7.3.1 without any issues, then adding later Win 10 patches should also not cause any issues. Of course, we cannot test every patch, especially retroactively for every release. So if you do notice any issues, please report them accordingly.
To be clear, if you are asking for client OS, overall windows 10 is supported - see the answers above by Rett. But if you actually means server OS (where Pega instances run), windows 10 is not officially listed there. What does that mean normally? Do not run mission critical applications on unsupported platforms.