[3.12] gh-128342: Specify timeout unit in subprocess docstrings (GH-128343) (#128366)

gh-128342: Specify timeout unit in subprocess docstrings (GH-128343)

Specify timeout unit (seconds) in subprocess docstrings
(cherry picked from commit dafe7a44630aa32bb411cceb45c7b7df725e3fe3)

Co-authored-by: n-l-i <57808975+n-l-i@users.noreply.github.com>
Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>