[docs] [issue40064] py38: document xml.etree.cElementTree will be removed in 3.9

Change by Chitrank-Dixit <chitrankdixit@gmail.com>: ---------- keywords: +patch nosy: +Chitrank-Dixit nosy_count: 2.0 -> 3.0 pull_requests: +20925 stage: -> patch review pull_request: https://github.com/python/cpython/pull/21784 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue40064> _______________________________________