[doc] Clarify that Popen.wait is only a busy-loop in certain cases

Documentation

In the docs for Popen.wait(), it states:

Note The function is implemented using a busy loop (non-blocking call and short sleeps). Use the asyncio module for an asynchronous wait: see asyncio.create_subprocess_exec.

This is actually only true in a specific circumstance: when both using Posix/Unix and a timeout is given. If, on the other hand, no timeout is given, then it does not go into a busy-loop but instead blocks on os.waitpid(). And for Windows, it never goes into a busy-loop, as it uses the WaitForSingleObject() windows API.

This note in the docs caused me to refactor my code to use asyncio - only later did I actually check what python did internally and discovered the note was wrong.

从 issue 中链接的 Popen.wait() 文档开始，并将该注释与此处描述的平台行为和 timeout 行为进行比较。修改该注释，将关于 busy-loop 的说法限制为带有 timeout 的 POSIX/Unix 等待，同时准确涵盖无 timeout 和 Windows 的情况。完成的标准是措辞在技术上正确，并保留 asyncio 指导。