Instead the standard executor will fall back to threads.
semfree caused test failures with Py3.14:
https://github.com/ocrmypdf/OCRmyPDF/issues/1558
In retrospect and with emerging Python tech like freethreading, semfree is becoming less necessary. We can use threads for the time being.
A consequence is that performance may be lower on Lambda and Termux when we are using threads and not shelling out work.