[3.12] Doc/library/os.rst: `os.waitid` absent on MacOS (GH-104558) (#113553)

Doc/library/os.rst: `os.waitid` absent on MacOS (GH-104558)

* Doc/library/os.rst: `os.waitid` absent on MacOS

(cherry picked from commit db1c88223986efe3076eb3b229a8b6db59bae284)

Co-authored-by: John Hawkinson <jhawk@alum.mit.edu>
Co-authored-by: AN Long <aisk@users.noreply.github.com>