[3.8] Doc: Add output to example code in programming FAQ (GH-21346) (GH-21791)

[3.8] Doc: Add output to example code in programming FAQ (GH-21346) (GH-21791)

Add output hint to document, part faq/programming, section [How do I write a function with output parameters (call by reference)?](https://docs.python.org/3/faq/programming.htmlGH-how-do-i-write-a-function-with-output-parameters-call-by-reference).

This patch make the output hint just like prefix code block.
(cherry picked from commit 67acf74c4eaf64a860cc1bcda6efe6e9cb01f89b)

Co-authored-by: Jiajie Zhong <zhongjiajie955@hotmail.com>
Automerge-Triggered-By: @merwok