gh-88324: Clarify documentation for redirected stdout/stderr when using subprocess in Linux (#94035)

* Update description of stdout, stderr, and stdin.

Changes:
- Move the ``None`` option (which is default) to the front of the list
  of input options
- Move the ``None`` option description up to make the default behavior
  more clear (No redirection)
- Remove mention of Child File Descriptors from ``None`` option description