[docs] [issue38413] Remove or change "Multithreading" section

Change by Vladimir Ryabtsev <greatvovan@gmail.com>: ---------- pull_requests: +22071 pull_request: https://github.com/python/cpython/pull/23159 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue38413> _______________________________________